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The Trimouns quarry: Luzenac, Ariege, France.

In recent decades, the Trimouns quarry has become well known as a source of outstanding crystals of several rare earth element-bearing minerals, including familiar species such as allanite, parisite and bastnasite, as well as very rare ones such as hingganite, iimoriite and dissakisite. Beautiful micromount-size specimens are the rule, but attractive crystals of several species exceeding 1 cm have also been found. These minerals occur in dolomite vugs in a contact zone of the Trimouns talc/chlorite deposit, where large-scale mining for talc may now be approaching its end.

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INTRODUCTION

The Trimouns talc-chlorite deposit is a mineral locality of international significance, producing fine crystal specimens of rare earth element-bearing species including allanite/dissakisite, bastnasite, synchisite, parisite, hingganite and iimoriite. Also, Trimouns is the type locality for two recently described species, trimounsite and gatelite.

The deposit is located in the Ariege Departement of southwestern France, 6 km northeast of the village of Luzenac, 40 km (via Spain) from the Principality of Andorra, and 115 km from Toulouse. It lies at an altitude of 1800 meters on the west slope of the St Barthelemy massif, the peaks of Saint Barthelemy (2348 meters) and Soularac (2368 meters) towering above it. Because of the heavy winter snowfalls, talc is quarried for only 6 months of the year, from May through October.

The name Trimouns comes from the langue d'Oc words Tres Monts (three mountains), in reference to the three peaks that overlook the quarry. Langue d'Oc is a regional language of Latin origin; it is traceable to the Middle Ages and is still spoken today in southern France, in the region known as Languedoc--the equivalent in northern France is langue d'oil.

HISTORY AND MODERN WORKINGS

The Trimouns deposit was first described in print in 1841 by Engineer Francois in the Annales Agricoles Litteraires et Industrielles de l'Ariege. In 1905 the quarry was acquired by the Societe des Talcs de Luzenac (Mengaud, 1909); in 1988 it was purchased by the Groupe Luzenac, a wholly owned subsidiary of Rio Tinto Zinc (RTZ), the world's foremost producer of talc at 1.3 million tonnes per year. The quarry employed some 100 workers at the beginning of the 20th century, when the ore was hand-sorted (de Launay, 1913). Today the talc is quarried by modern hydraulic shovels, and the ultra-white ore is sorted by laser camera.

Trimouns, the largest talc occurrence in France, possesses estimated reserves of 16 million tonnes, sufficient for half a century. The quarry employs 300 people and is the largest talc-chlorite mine in Europe, producing more than 400,000 tonnes annually.

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The ore is quarried both mechanically (85% of the tonnage) and manually from successive benches. The ore is then sorted, partly on the basis of their degrees of whiteness (see below). Each year 10.35 million cubic meters of waste rock are extracted by a 210-tonne mechanical shovel with a 25-tonne capacity bucket. The rock is loaded into 8 dumpers at a rate of 16 tonnes/hour; each dumper has a transport capacity of 120 tonnes/day.

The mine cars, each with a 1 cubic meter capacity, are filled with talc and then transported by cable car from the quarry to the processing plant in the valley 5.5 km away. The altitude difference is 1100 meters and the journey takes 24 minutes.

Eighteen grades of ore are distinguished on the basis of two criteria: chemical composition and whiteness. The chemical composition corresponds to the distinction between dominantly talcose and dominantly chloritic ore, and to the amount of barren inclusions (unaltered rock: residual dolomite, pegmatite and mica schist). The degree of whiteness is assessed visually by the seasonal laborers, mainly Moroccans and Portuguese. About 80 of these workers extract and sort some 300 kg of ore per hour on each mine bench; this manually extracted ore represents 15% of the total ore tonnage produced. Optical laser sorting in the storage plant over the past few years has significantly increased the yield. A laser beam sorts each bit of talc by analysing its whiteness and directs a jet of compressed air to offload it from the conveyor belt at the correct place.

Talc is used in the manufacture of paper, polymers, paint, cosmetics and pharmaceuticals, ceramics, foodstuffs and fertilizer, among other things.

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GEOLOGY

The Pyrenees Mountains are the product of two superimposed orogenies, the Hercynian Orogeny during the Paleozoic and the Alpine Orogeny during the Tertiary. The mountains, forming a natural barrier between France and Spain, extend for almost 600 km in a generally east-west direction, from the Gulf of Lions, in the Mediterranean Sea, to the Bay of Biscay, in the Atlantic Ocean.

The Saint Barthelemy massif is composed of three major units, in places separated by unconformities: a basal gneiss unit, a migmatite unit overlain by a mica schist envelope, and finally a weakly metamorphosed Paleozoic succession. The talc deposit lies at the contact between the crystalline gneiss and the heterogenous migmatite of the Saint Barthelemy massif and its epimetamorphic cover rocks. At the contact with the mineralized orebody, these cover rocks are represented by Ordovician chlorite-graphite schist with thick dolomitic intercalations.

The basal gneiss unit of the massif has an apparent monoclinal structure with a slight northerly dip, and can be subdivided into three types defined by their structural features and their parageneses. From base to top, these are (1) migmatitic gneiss, (2) augen gneiss characterized by a fairly constant blastomylonitic texture probably related to shear movements, and (3) intermediate gneiss that has preserved the augen structure but has apparently undergone slight migmatization.

The migmatite unit is heterogeneous, ranging from metatexite to diatexite facies, and incorporates leucocratic muscovite granite bodies.

The weakly metamorphosed Paleozoic succession includes all the Paleozoic formations that can be dated either by their fossils or by their facies analogies. The oldest formations datable through facies are Ordovician; these are conformably overlain by Silurian, Devonian and Carboniferous units.

Ordovician rocks are ubiquitous on the northern edge of the Saint Barthelemy massif. A typical succession from the base up is:

(1) Sandstone (100 meters): decimeter to centimeter-thick interbeds of schist and fine-grained sandstone.

(2) Carbonate-sandstone (0-80 meters): alternating decimeter-thick to meter-thick beds of sandstone and dolomitic limestone.

(3) Pale schist-sandstone (0-200 meters)

(4) A very fine-grained limestone-sandstone (5 meters) that, because of its consistency, makes a very good stratigraphic marker.

(5) An upper carbonate unit (100-150 meters) showing major and rapid facies variations.

(6) An upper schist unit (0-100 meters) rich in phyllite (chlorite-sericite).

Silurian rocks are mainly represented by black oil shale with varying amounts of organic matter: this appears to be a homogeneous unit deposited under euxinic conditions.

Devonian rocks occur in a thick succession (400-500 meters) that is clastic at the base and essentially carbonate at the top.

Four successive phases of regional Hercynian deformation are recognized in the Pyrenees; these have been designated as D1 through D4:

Phase D1 was very discrete in the vicinity of the Saint Barthelemy massif. In the sub-Paleozoic terrain it has generally been obliterated by the later phases and associated major recrystallization.

Phase D2 gave rise to the main structures of the massif. It affected the various horizons differently, metamorphosing sedimentary units to different degrees.

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Phase D3. the most apparent in outcrop, corresponds to the peak terminal phase of the migmatization in the deepest levels, with constant interaction between the folds of the sediments and the pegmatite injections.

Phase D4 is reflected in the mica schist and migmatite by very broad (10 to 100 meters wavelength) folds, with an axial plane that is either vertical or slightly west or east-dipping. Most of the thrusts and brittle faults in the region can be assigned to this phase.

Locally, in the Trimouns quarry area, five tectonic phases have been determined; these have been designated as P0, P1, P2, P3 and P4:

Phase P0 (=D2) corresponds to the development of the cleavage or foliation of the rocks during the major Hercynian metamorphism. It was at this stage that the metamorphic zoning of the schistose envelope took place, ranging from sillimanite facies at the footwall to muscovite-chlorite and chlorite-sericite facies at the hanging wall. The migmatization of the mica schist was accompanied by the emplacement of pegmatite bodies.

Phase P1 (=D3) at the footwall is represented by very supple flow-microfolding on a 10-cm to 10-meter scale, deforming the pegmatite veins. In general the axis of these folds, striking northsouth, is horizontal. In the epimetamorphic schist of the hanging wall, this movement is marked by meter-long to 10-meter-long folds with an axial strike of N40[degrees].

Phase P2 (=D4) is a phase of large-radius (10 to 100 meters) folding, rarely observed in outcrop but evident from stereographic analysis, particularly in the footwall mica schist.

It should be noted that a spatial stress-related zoning is observed for P0 to P2, with greater intensity at the base than at the top of the structure. A time-related zoning is also evident in the variable intensity of deformation, with the following deformations at the footwall: (1) flux and plastic flow at P0; (2) axial cleavage and plastic deformation at P1; and (3) broad deformation with no foliation at P2.

Phase P3 (= D4) is the last major phase in the thrust of the hanging wall over the footwall, producing specific physiochemical conditions that favored alteration of the mineralization. This phase was responsible for a major reduction in the thickness of the metamophosed Paleozoic units, for the imbrication of most of the units in the thrust plane, and for the permeability favoring the circulation and action of hydrothermal fluids.

Phase P4 corresponds to the Late Hercynian, or Pyrenean, movements. The major movement of this phase was a relative sinistral (leftward) flow of the hanging wall with respect to the footwall. "This phase was responsible for the large thickness variations in the deposit, locally stretched and laminated and elsewhere broadened to give a boudinaged lenticular aspect" (Pinato, 1999).

The structure corresponds to a decollement plane of the epimetamorphic cover over the foliated metamorphic rock, giving rise to irregular alternating layers of talc and chlorite.

The formation of the deposit resulted from a telescoping of geological events, i.e. the last Hercynian phase of folding, the overthrusting of the basement by the cover rocks with lamination of the dolomite and country rock, the percolation of magnesian hydrothermal fluids and chloritization of the aluminosilicate facies (mica schist, aplite, pegmatite), and finally metasomatic "talcification" of the dolomite and siliceous rocks.

The talcose mineralization has a close relationship with the magnesian unit of the hanging wall.

The mineralized (talcose-chloritic) formation, trending North-South to N10E[degrees] with an easterly (25[degrees] to 80[degrees]) dip, lies between the foliated metamorphic rocks of the footwall (gneiss, heterogenous migmatite) and the pelitic formations, with dolomitic intercalations, of the hanging wall. Its thickness varies from 20 meters at the ends to more than 80 meters in its central part. All of the rare-earth minerals come from this zone (Fortune, 1971; Fortune et al., 1987; Gatel, 1990).

Footwall rocks (Cambrian): The footwall consists of pegmatite and calc-silicate gneiss overlain by a few thrust outliers of mica schist or aluminosilicate formations in contact with the chloritic mineralization.

Hanging-wall rocks (Late Ordovician carbonates): The hanging wall is composed of dark-colored to black chlorite-graphite schist with thick, variably metamorphosed, intercalations of dolomite that in places has a banded or striped apppearance. Locally this formation can harbor a vuggy fracture zone.

The suite of rare-earth element-bearing minerals present at Trimouns is remarkable, and is of great scientific interest for the study of how rare-earth elements are distributed among the different mineral families (carbonates, silicates, etc.) under low-temperature hydrothermal conditions. Thermometric and fluid-inclusion studies of chloritic and scarce apatite ore have revealed that the formation temperature of the deposit was 320[degrees]C for a pressure of 2.5 kbar (Parseval, 1992). The age of the deposit, as determined by U-Pb chronometry on samples of xenotime and monazite (Scharer et al., 1999), is between 97 and 112 million years.

WHAT ARE "RARE EARTHS?"

The Rare Earths form a group of 17 elements in the Periodic Table accounting for approximately one-sixth of all the known elements. These include scandium, yttrium, lanthanum and the lanthanides. The term "Rare Earths" derives from the fact that these elements were not predictable and had not yet been discovered when Mendeleev derived the Periodic Table; thus they were considered rare when they were discovered.

All of the Rare Earth elements occur naturally, with the exception of the unstable promethium, a product of uranium fission. Moreover, the qualifier "rare" is actually not justified for most of these elements, some of which, such as cerium, lanthanum and neodymium, are more common than lead in the Earth's crust (Forret and Pomerol, 1954).

Most of the rare earths are "transition" elements, characterized by the fact that the electron sublayers d or f are filled after the higher sublayers s and p. In the cases of scandium (atomic number 21) and yttrium (atomic number 39), these are, respectively, sublayers 3d and 4d. For the lanthanides, starting at cerium, it is sublayer 4f (lanthanum is not a transition element).

This anomaly in the filling of the sublayers is explained by the energy of the atomic orbitals in relation to the number of protons and neutrons in the nucleus. As a consequence of this anomally, the trivalent ions formed by the various Rare Earth elements (through the loss of the outer electrons s and d) all have the same remaining outer electron envelope (corresponding to xenon for the lanthanides). It is therefore impossible to separate the Rare Earths chemically; this problem was only understood through the efforts of the Manhattan Project.

The physical properties of the Rare Earths effectively depend on the total number of 4f electrons, and thus the properties vary. In the solid state, lanthanum and the lanthanides preserve the free atom properties that they share with the actinides in the Periodic Table. Among other things, the ionic radii decrease slightly with increasing atomic number (this phenomenon is called the lanthanide contraction). The lanthanide ions thus possess discrete energy levels, both in solution and in solids, which cover the entire wavelength spectrum from infrared to violet. Industry exploits these energy scales, e.g. for the phosphor dots of television screens, fluorescent tubes, lasers and energy converters.

Certain lanthanide ions are paramagnetic and can give rise to interactions. Alloys containing Rare Earth elements can make very powerful permanent magnets that are increasingly in demand.

The Rare Earths now play major roles in advanced technologies. This is a continuing process, and the extent of industrial consumption of Rare Earths is a good indication of a country's technological level (Caro, 1994).

MINERALS

The Trimouns deposit has been the subject of many publications since the mid 19th century, and our knowledge of the mineralization improves with each new study (Capdecomme, 1950; Zwart, 1954; Thiebaut et al., 1965, 1966, 1968; Aranitis, 1967; Artigue, 1978; Fortune et al., 1980, 1986; Moine et al., 1989).

The deposit consists of alternating dominantly talcose and dominantly chloritic layers. It extends over a strike length of 1.5 km and varies in thickness between 20 meters and 80 meters, such that the mineralization has a boudinaged, lenticular appearance. The variation in thickness is due to deformations of the hanging wall, with a flow of the mineralized unit along the broad folds.

The mineralogical uniqueness of the Trimouns deposit is due to the presence of Rare-Earth-Element (REE) minerals in the hanging wall of the talc-chlorite structure. These are found in dolomite vugs and microfissures reminiscent of the Alpine type (Laforet et al., 1980; Descouens and Gatel, 1987; Parseval et al., 1997). However, no equivalent deposit is found in the standard literature on Alpine fissures (Desbuissons, 1909; Niggli et al., 1940; Parker, 1954; Stalder et al., 1973; Gramacioli, 1977; Weibel, 1990; Albertini et al., 1993); not even the classic Lengenbach deposit in Valais, Switzerland, with crystals in a dolomite gangue, is comparable, and REE-bearing pegmatite zones, such as those of Greenland, do not contain a similar paragenesis (Petersen and Secher, 1993). And yet the style of Trimouns crystal specimens resembles that of specimens from Alpine fissures: isolated crystals in matrix, having an aesthetic appearance highly valued by collectors.

Aeschynite-(Y) (Y,Ca,Fe,Th)(Ti,Nd)[.sub.2](O,OH)[.sub.6]

Aeschynite is found in the hanging wall of the talc-chlorite mineralization zone, filling saddle-dolomite vugs commonly associated with calcite. Three habits are present: (1) transparent prisms averaging several millimeters in size, pinkish brown to yellowish brown, in places straw-colored, forming groups of interlaced individuals and more rarely isolated crystals; (2) tabular crystals up to 4 cm long and less than 1 mm thick, orange-beige in color, sprinkled with millimeter-size euhedral crystals of "limonitized" pyrite; and (3) orange-yellow acicular sprays.

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Electron probe microanalysis of a yttriferous aeschynite gave the ideal formula [Ti.sub.2] (REE)(O,OH)[.sub.6]. The unit cell is a = 5.174, b = 10.76, c = 7.59. Of note is the presence of yttrium, gadolinium, samarium, neodymum, and dysprosium (Deliens, 1991; Zappel and Leverkusen, 1986).

Albite NaAl[Si.sub.3][O.sub.8]

Albite is asociated with slightly smoky quartz. Most of the crystals come from the footwall in the talc-chlorite zone, though the mineral is also found in the hanging-wall pegmatite of the talc structure. The albite crystals are several millimeters to 1 cm in size, translucent, and white to colorless; some are twinned.

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Allanite-(Ce) and/or Dissakisite-(Ce)

(Ca,Ce,La)[.sub.2](Al,[Fe.sup.2+],[Fe.sup.3+])[.sub.3][Si.sub.3][O.sub.12](OH)

Ca(Ce,La)Mg[Al.sub.2](Si[O.sub.4])[.sub.3](OH)

Allanite and dissakisite are chemically similar, and are distinguished primarily on the basis of the Fe:Mg ratio. Individual crystals tend to be rather homogeneous; many line scans carried out by a scanning electron microscope (SEM) analysis of a crystal and the corresponding diffractogram for the same crystal demonstrate this (Pinato, 1999). Dissakisite was first discovered at Balchen Mountain, Antarctica (Grew et al., 1991).

Allanite from Trimouns was described by Moelo et al. in 1974 and identified by X-ray diffraction and qualitative analyses. Chemical analysis shows that it is a magnesium-bearing allanite that occurs as elongate crystals, and more rarely as flattened prisms; it is associated with the banded dolomite with intercalated millimeter-thick graphitic beds, and with white crystalline dolomite. The translucent crystals, with generally smooth (more rarely rough) faces, are brown, reddish brown, purplish brown, greenish brown, and pale brown to pale chestnut. They are found in a gangue of white to gray dolomite and as doubly terminated "floater" crystals in geodes and vugs (of several centimeters) in talc that has crystallized into translucent folia. Some crystals show growth phantoms. It would appear that when the color is pale the species is dissakisite and when the color is darker the mineral is probably allanite.

Allanite and dissakisite form isolated crystals to 6.5 cm long and a few millimeters thick, and as groups of enmeshed individual crystals each several millimetres in length. The crystals can show etch figures indicating that conditions changed near the end of the crystallization; these figures could be confused with signs of incipient metamictization, but the mineral is not metamict. The crystals are invariably pleochroic, as are all crystals of the minerals of the epidote group.

Allanite/dissakisite can be associated with bastnasite, synchisite, parisite, quartz, calcite, and very rarely with hingganite. It is the most common REE species in the Trimouns deposit and has been consistently found since the appearance of the first REE minerals in the hanging wall of the talc-chlorite zone, in the hydrothermally altered zone at the contact of the dolomite (top part of the lenses) with Ordovician black shales.

Almandine [Fe.sub.3.sup.2+][Al.sub.2](Si[O.sub.4])[.sub.3]

Red-brown to dark brown almandine crystals from 1 mm to 1 cm occurs in the pegmatite zone in the footwall.

Anatase Ti[O.sub.2]

Anatase occurs in the hanging wall of the talc-chlorite mineralization, in white saccharoidal dolomite. It is very rare in the deposit, and only a few specimens have been found. The crystals are everywhere less than 1 mm in size and brown in color. Identification was by Raman spectroscopy.

Aragonite CaC[O.sub.3]

Aragonite was found in 1987 in the footwall of the talc structure, forming whitish to beige, acicular, stalactitic crystals in a fracture zone in contact with indurated black rock. Rare radial sprays, less than 1 mm in size, have been reported in geodes in dolomite, in the hanging wall of the talc structure.

It has been found in association with pyrite.

Arsenopyrite FeAsS

Around 1900, arsenopyrite was reported as forming crystalline masses, with rare millimeter-size crystals, near the footwall of the talc mineralization in contact with pegmatite associated with quartz. The following faces were noted: {100}, {011}, {101} and {001} (Lacroix, 1896). Arsenopyrite has not been seen at the deposit since then.

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Bastnasite-(Ce) (Ce,La)(C[O.sub.3])F

Three types of bastnasite have been found at the site. Most commonly it occurs as brown to orange-red, hexagonal prismatic crystals, exceptionally to 3.5 cm long and several millimeters thick, with {10[bar.1]0} and {0001} as the main forms. The best specimens were collected in 1985 and 1986.

Thin-tabular hexagonal crystals to several millimeters across also belong to this first type. Aggregates of these crystals may be parallel-growth stacks or regularly offset clusters up to 3 cm across, similar to the "iron roses" of Alpine hematite. Isolated, pale pink tabular crystals to 1 mm are also found.

The second type consists of columnar bastnasite-(Ce) crystals, some of them partially gemmy, less than 1 mm thick but reaching 2 cm long. Their color varies from orange-yellow to reddish brown.

In the third type, bastnasite-(Ce) forms squat, orange-red to brown, hexagonal crystals reminiscent in form of the vanadinite crystals of Morocco; they also resemble the generally more elongated bastnasite crystals of Zegi Mountain, Northwest Frontier Province, Pakistan. The best crystals of this type reach 6 mm long.

All of these crystals are found in vugs or in fissures in calcite within a crystalline dolomite marked by bands of dark blue to blackish graphite a few millimeters thick. The vugs are located in the footwall of a fractured area within the hydrothermally altered zone, near its contact with the black shales forming the hanging wall of the talc mineralization.

Bastnasite-(Ce) crystals of the first type are commonly found in association with allanite and/or dissakisite, and less commonly with quartz (Doll, 1983). A particularly remarkable association should be noted: it consists of millimeter-size flakes of bastnasite deposited as a crown around synchisite (a syntactic intergrowth). These specimens are found in gangue of whitish to bluish-gray crystallized dolomite, more rarely on calcite crystals (some of the "nailhead spar" habit), or on talc crystallized as nacreous flakes lining pockets many centimeters across.

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Brookite Ti[O.sub.2]

Brookite occurs in the same environment as the anatase and rutile and has an identical paragenesis; it is visually distinguishable from the two polymorphs. The crystals are brown and less than a millimeter in size (Favreau, 1994).

Calcite CaC[O.sub.3]

Abundant in the deposit, calcite occurs as isolated crystals or in attractive clusters. Prismatic crystals of varying length/width ratios reach 20 cm long, and often display the classic "nailhead" form (Lacroix, 1962). Crystals twinned on (0001) or (02[bar.2]1) may be several cm long. Calcite crystals are commonly perched on a matrix of rhombohedral dolomite, including curved, saddle-shaped dolomite crystals, and more rarely on crystalline talc. Large "floater" crystals of calcite were discovered in 1983. Rarely pinkish violet in color, the crystals fluoresce green in shortwave ultraviolet light, and are in some cases associated with quartz.

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Cassiterite Sn[O.sub.2]

Cassiterite occurs as elongated, translucent dark brown tetragonal prisms of the "needle tin ore" type. The crystals average several millimeters long, a few exceeding a centimeter, and the terminations are formed by pyramidal faces {111} or {101} in combination with {110} and {100} respectively.

Large euhedral crystals as much as 3.5 cm long were found in 1994 associated with flakes of talc.

Astonishing yellow-brown cassiterite crystals, commonly twinned and partially of gem quality with darker zones near the tops of the crystals, were found in 1995 in the hydrothermally altered part of the hanging wall. They were collected from a vug near a fracture zone, associated with calcite and more rarely quartz. The same environment yields colorless to yellowish, millimeter-size crystals, as well as very rare dark brown, twinned crystals several millimeters in size, with flat terminations, resembling ekanite crystals.

Chabazite-Ca [Ca.sub.2]([Al.sub.4][Si.sub.8][O.sub.24])*13[H.sub.2]O

Chabazite crystals from the deposit are white, translucent, and average several millimeters in size; they are commonly confused with dolomite. They come from the foliated metamorphic rocks in the footwall of the talc-chlorite structure, often in association with stilbite and pyrite (Favreau, 1994). Penetration-twinned crystals are common.

Chalcopyrite CuFe[S.sub.2]

Chalcopyrite has only been identified visually thus far, and so the identification remains uncertain. The crystals are poorly formed (in places as pseudo-scalenohedrons), rarely reach a millimeter in size,

and may be associated with aragonite. They come from the footwall of the talc-chlorite mineralization in dark indurated rocks close to the contact with the pegmatite zone (Favreau, 1994). In spite of many searches, the mineral has not been found since the mid-1990's.

Chlorite Group (Mg,[Fe.sup.2+],Al)[.sub.6][(OH)[.sub.8]I(Al,Si)[.sub.4][O.sub.10]]

Crystals of an unidentified chlorite-group mineral several millimeters in size are found in the footwall of the hydrothermal zone close to the contact with the pegmatites and in the same environment as the clinochlore. They form dark-green tablets and vermiculate spherules as much as 2 cm in diameter (De Parseval et al., 1991). One can find it in association with apatite, titanite, talc and rutile.

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Clinochlore (Mg,Al)[.sub.6](Si,Al)[.sub.4][O.sub.10](OH)[.sub.8]

The minerals of the chlorite group are widely represented in the zone close to the footwall of the talc-chlorite structure. Clinochlore occurs in its vermicular form in felted masses with curious subaerial shapes, commonly reaching 2 cm in length for a diameter of less than a millimeter, in a dolomitic gangue. It is also found in the hanging wall of the structure associated with bastnasite and very rarely with thortveitite.

Clinozoisite [Ca.sub.2][Al.sub.3][Si.sub.3][O.sub.12](OH)

Clinozoisite was found in 1986 in the chloritized zone of the footwall of the talcose structure, as colorless, millimeter-size prisms with a nacreous luster; the crystals are striated longitudinally and in places show a {001} termination.

Diopside CaMg[Si.sub.2][O.sub.6]

Diopside is reported in the footwall of the talc structure, forming millimeter-size tabular crystals associated with chlorite.

Dissakisite-Ce (see Allanite)

Dolomite CaMg(C[O.sub.3])[.sub.2]

Dolomite is the most abundant mineral in the deposit. It is commonly found crystallized in lenses in the hanging wall, and as saddle-shaped crystals, several millimeters to several centimeters in size, lining the bottoms of geodes, vugs and joints (1st generation), and as undistorted rhombohedral crystals several centimeters in size, perched on the saddle-shaped crystals (2nd generation). Twinning of crystals on (0001) is common.

Dolomite is commonly found in association with calcite and quartz, and is almost always the matrix hosting crystals of bastnasite, synchisite, and allanite and/or dissakisite.

Epidote [Ca.sub.3][Al.sub.2]([Fe.sup.3+],Al)[Si.sub.3][O.sub.12](OH)

Epidote has been found in a loose block at the entrance of the quarry, but has never been found in situ. However, tornebohmite and gatelite, with similar chemical compositions, have been collected in the quarry.

Ferrocolumbite-Ferrotantalite [Fe.sup.2+][Nb.sub.2][O.sub.6]/[Fe.sup.2+][Ta.sub.2][O.sub.6]

Brown-black to red-brown patches and aggregates a few tenths of a millimeter in size, coming from pegmatite and granitoid in the hanging wall of the talc-chlorite structure, were found in 1992. Microprobe analysis and thin-sections from the chloritized zone confirm that the species is part of the ferrocolumbite-ferrotantalite series (Gatel, personal communication, 2001).

Fluorapatite [Ca.sub.5](P[O.sub.4])[.sub.3]F

A few colorless, millimeter-size crystals of fluorapatite were found in 1986. They came from the footwall of the talc structure in the chloritized zone close to the pegmatite.

Galena PbS

Found in the deposit in 1998, galena occurs as patches of several millemeters filling very small vugs in dolomite in the hanging wall of the structure. Visual identification of the material as galena was made on the basis of its bluish gray color, its metallic luster and its perfect cubic cleavage.

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Gatelite-(Ce) (Ca,RE[E.sub.3])[.sub.4][[Al.sub.2](Al,Mg)(Mg,Fe,Al)][.sub.4][[Si.sub.2][O.sub.7]][Si[O.sub.4]][.sub.3](O,F)(OH,O)[.sub.3]

Gatelite-(Ce) is a new mineral species described by Guy Bernadi and Freddy Marty in 1998, and named for M. Gatel, a French amateur mineralogist (AFM).

The mineral, which has not yet been found in situ, comes from vuggy blocks of pale crystalline saddle-shaped dolomite, and forms groups of crystals up to 1.6 mm in size. The crystals are colorless to whitish, resembling very pale dissakisite, and display longitudinal striations. The samples appear to come from the upper part of the hydrothermally altered lens in the hanging wall of the talc-chorite structure.

Some crystals are found in association with chlorite. These are easily confused with crystals of clinozoisite, but do not occur in the same paragenesis.

Goethite [alpha]-[Fe.sup.3+]O(OH)

Goethite is found in massive, locally earthy aggregates near the talc lens.

Graphite C

Graphite is abundant in the quarry, particularly in the hanging wall of the talc-chlorite structure. It forms millimeter-thick, black, amorphous layers interbedded with very pale crystalline dolomite, imparting a banded or striped appearance. It also occurs as shiny black 10-cm amygdules. More rarely, isolated flat fibers of graphite several millimeters long have been reported.

Gypsum CaS[O.sub.4]*2[H.sub.2]O

Massive gypsum, a byproduct of the decomposition of pyrite, occurs intermixed with calcite and talc; colorless, millimeter-size crystals have also been found. Species determination was made by analysis with the scanning electron microprobe (SEM) (G. C. Parodi, pers. comm.).

Halite NaCl

Halite, as granular aggregates included in quartz, was identified by electron microprobe (Parodi, pers. comm., 1998).

Hellandite-(Y) (Y,Ca)[.sub.6](Al,[Fe.sup.3+]) [Si.sub.4][B.sub.4][O.sub.20](OH)[.sub.4]

Hellandite forms pale pink, tabular hexagonal crystals less than 1 mm in size, with a pronounced nacreous luster. It is very rare in the deposit, having been identified by X-ray diffraction on a few samples from the quarry dump. It is not thus far been seen in situ. The mineral was reportedly found only once, and its authenticity appears doubtful.

Hematite [alpha]-[Fe.sub.2][O.sub.3]

Hematite is found very rarely as millimeter-size euhedral crystals forming rosettes and pseudomorphs after pyrite associated with saddle-shaped dolomite crystals.

[FIGURE 27 OMITTED]

Hingganite-(Y) (Y,Yb,Er)[.sub.2][Be.sub.2][Si.sub.2][O.sub.8](OH)[.sub.2]

Hingganite occurs as isolated, prismatic, translucent crystals and also as fan-shaped groups from a few millimeters to 1 cm long, with a pale-green to pale-yellow color (Voloshin et al., 1983; Miyawaki et al., 1984, 1990). The samples were found between 1990 and 1993.

Crystals ranging in color from greenish to yellowish to pale beige or pale gray-green were discovered in 1986 in vugs in crystalline dolomite. Some crystals show bevelled terminations as well as truncations on the top faces of the crystals, i.e. the basal pinacoid faces. Rare in the deposit, hingganite-(Y) is part of the dolomitic metasomatic suite from the hanging wall of the talc structure. It is found in the same environment as iimoriite. This hingganite has a very low iron content (analysis by Dr. G. Parodi).

[FIGURE 28 OMITTED]

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[FIGURE 30 OMITTED]

[FIGURE 31 OMITTED]

[FIGURE 32 OMITTED]

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Iimoriite (Y) [Y.sub.2](Si[O.sub.4](C[O.sub.3])

Iimoriite was previously only known as 3-cm crystalline masses in a pegmatite at Kawatamanachi, Fukushima Prefecture, Japan (Kato and Nagashima, 1970) and in a granite massif at Bokan Mountain, Prince of Wales, Island, Alaska (Foord et al., 1984).

At Trimouns iimoriite generally occurs as pink to colorless, 2 to 3-mm, pink to colorless crystals, some showing gemmy areas, in crystalline dolomite. The crystals are tabular, slightly curved, and longitudinally striated; they occur in matrix of white saccharoidal or saddle-shaped dolomite, most commonly as isolated singles, but occasionally in small groups. Some doubly terminated "floater" crystals of iimoriite-(Y) up to 1 cm in size have been found in vugs in crystalline talc; in rare cases crystals to 1 mm are twinned. X-ray determination of the internal structure of iimoriite gives the following unit cell parameters: a = 6.573 b = 6.651 c = 6.454.

[FIGURE 34 OMITTED]

[FIGURE 35 OMITTED]

[FIGURE 36 OMITTED]

Iimoriite is farly rare in the deposit. Well-formed crystals are found in the hanging wall, in fissures in banded dolomite of the upper part of the carbonate lenses. It is commonly associated with thortveitite and is found in the same environment as hingganite.

The medium to dark pink color of certain iimoriite crystals does not show up well in photographs and becomes greenish on printing (luminescence and probable radioactivity).

The best known crystal measures 1.7 cm long. It is doubly terminated, and was found loose in a vug in talc in 1997. It is extraordinary, and no comparable crystal has been found since.

"Limonite" mixture of hydrous iron oxides

Limonite results from the alteration of pyrite, after which it forms pseudomorphs. These pseudomorphs occur as isolated crystals ranging up to 10 cm in size, and as groups of subhedral crystals associated with allanite and/or dissakisite, aeschynite, synchisite, parisite, bastnasite and, more rarely, cassiterite.

The iron hydroxides and oxides, with their ocher to brown color, commonly contrast with the white or gray dolomite, locally imparting touches of bright color that seem to spread out over the exposures in the hanging wall of the talc structure.

Malachite [Cu.sub.2](OH)[.sub.2]C[O.sub.3]

Early in the history of the quarry, malachite was reported as forming millimeter-size encrustations and films in joints in the beige dolomite of the hanging wall of the talc-chlorite mineralization. The mineral has not been seen in the deposit since 1903.

Microcline KAl[Si.sub.3][O.sub.8]

Microcline has been reported in the pegmatite zone of the footwall of the talc-chlorite structure, where it forms masses of several millimeters, in places associated with chlorite, quartz and titanite.

Monazite-(Ce) (Ce,La,Nd) P[O.sub.4]

Monazite is present as isolated crystals from several millimeters to 1 cm in size, and more rarely as groups of crystals, in fine-grained white or graphitic dolomite of the hanging wall of the talc structure. It is orange to reddish brown, and the translucent crystals very commonly contain reddish inclusions. A few millimeter-size gem crystals with {100} and {111} terminations were found in 1987. The crystals are implanted on whitish dolomite in small vugs or microfissures, occasionally associated with rutile. Some monazite crystals, several millimeters in size, are sprinkled with 1-mm crystals of limonitized pyrite. Analyses give an age for the monazite of 99 [+ or -] 1 Ma (Scharer et al., 1999).

[FIGURE 37 OMITTED]

[FIGURE 38 OMITTED]

Muscovite K[Al.sub.2][square]Al[Si.sub.3][O.sub.10](OH)

A few lamellar crystals of muscovite several millimeters in size were collected in 1983 in the pegmatite zone of the hanging wall. Sharp pseudohexagonal prisms to 2 mm have been found in fissures in the mica schist.

Natrolite [Na.sub.2][Al.sub.2][Si.sub.3][O.sub.10]*2[H.sub.2]O

Natrolite forms white sprays of acicular crystals to 1 mm, the individual crystals having a square cross-section. It was discovered in 1985 in the mine dumps, in association with calcite. It has never been found in situ in the deposit.

Palygorskite (Mg,Al)[.sub.2][Si.sub.4][O.sub.10](OH)*4[H.sub.2]O

Palygorskite is found in dolomite joints as millimeter-size, white, silky fibers arising from the alteration of the phyllosilicates. The samples are all very fragile. They may be assocaited with allanite or bastnasite.

[FIGURE 39 OMITTED]

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Parisite-(Ce)Ca(Ce,La)[.sub.2](C[O.sub.3])[.sub.3][F.sub.2]

Parisite forms reddish brown to orange, hexagonal crystals tapering upwards; some crystals are horizontally striated, and some are translucent with gemmy areas. The crystals can be as much as 2.8 cm long and several millimeters thick. Parisite is found in the same environment as bastnasite, in units of crystalline dolomite interbedded with dark green to black shale a few hundred meters from the main contact. Parisite is very similar chemically to synchisite, and distinguishing them analytically is difficult (Lasmanis, 1977); however, parisite crystals characteristically taper to a point and synchisite crystals do not.

Very rarely, parisite crystals to several milimeters long are found to be terminated by {10[bar.1]4} faces; these could be confused with squat crystals of bastnasite.

Phlogopite K[Mg.sub.3]Al[Si.sub.3][O.sub.10](OH)[.sub.2]

Phlogopite is found as crystalline masses and as variably distinct aggregates at the contact with aplites in the footwall of the talc-chlorite structure, and also as palm-shaped crystals, several millimeters in size, in the marble limestone of the hanging wall.

Pyrite Fe[S.sub.2]

It is pyrite that made the Trimouns deposit famous at the beginning of the 20th century, after Lacroix (1896) reported the presence of curved-faced octahedral crystals several centimeters in size. The talc structure in the deposit commonly contains pyrite as very shiny, euhedral cubic crystals to 1 cm within the white massive talc. These crystals are often oriented in parallel within the massive talc, thus marking and emphasizing tectonic movements.

The largest pyrite crystals, with edges to 15 cm, were found in the 1960's. They came from the hanging wall of the talc-chlorite structure, in the dolomite that the local quarry workers call "little granite." This type of dolomite is formed of equidimensional grains, 1 to 5 mm in size, that resemble agglomerated salt crystals with faces {210}, {100} and {211}. The same environment also contains (1) octahedral pyrite crystals of several centimeters, locally associated with calcite, (2) exceptional dodecahedral pyrite crystals, commonly "limonitized" (supergene alteration), and (3) flat crystals elongated along the two-fold axis (pseudo-rhombic) or, more rarely, elongated along the three-fold axis (pseudo-rhombohedral). From these pyrite crystals we can see the influence of the enclosing matrix on the crystal form. Other form combinations encountered in the commonly "limonitized" crystals, several centimeters in size, are the cuboctahedron, the cubo-dodecahedron, the pyritohedron/dodecahedron and the pyritohedron/octahedron (Gatel, 1990).

Pyrrhotite [Fe.sub.1-x]S

Pyrrhotite nodules weighing several kilograms were reported at the beginning of the 1900's. The pyrrhotite came from the hanging wall of the deposit in highly metamorphosed, crystalline limestone beds, where it forms diffuse aggregates and rare millimeter-size gray-brown to black hexagonal crystals associated with milky white quartz (Lacroix, 1962). The mineral has since only been found as inclusions in calcite.

Quartz Si[O.sub.2]

In the hanging wall of the talc-chlorite structure, the best quartz crystals, generally isolated, are found in vugs, several tens of centimeters to more than a meter in size, in white, coarsely crystallized dolomite (Auriol, 1987). The crystals have a Bambauer (lamellar) structure and can reach 35 cm in length. Commonly they are transparent and colorless, and as beautiful as any quartz crystals from Brazil or from the La Gardette mine or other Alpine localities. In addition to the classical prismatic habit, some crystals display a typical pyramidal "Muzo habit," or are Dauphine twins.

A few centimeter-size clusters of quartz crystals were found in 1989, and some very good crystals were collected in 1994 at the contact of a talc lens with white crystalline dolomite.

Good doubly terminated "floater" crystals to several centimeters have also been reported, and, very rarely, some Japan-law twins, also to several centimeters.

Many quartz crystals from the deposit are curved, having been tectonically deformed (Lacroix, 1891). Growth phantoms outlined by whitish inclusions have been seen in some crystals.

[FIGURE 44 OMITTED]

The quartz can be associated with crystals of purplish calcite (to several centimeters), dolomite, allanite, bastnasite, synchisite, rutile and very rarely hingganite. A few patches of smoky quartz associated with crystals of albite several millimeters in size were found in 1997 in the footwall pegmatite zone of the talc-chlorite structure.

[FIGURE 45 OMITTED]

Rutile Ti[O.sub.2]

Rutile, as prismatic-acicular crystals from a few millimeters to 3 cm long and a few microns thick, and as black, centimeter-size sheaflike crystal aggregates, is found in the hanging wall of the talc-chlorite structure.

More rarely, rutile occurs as squat crystals to several millimeters, twinned on (011) (Bariand et al., 1978); these dark brown crystals are longitudinally striated, and the twins are of characteristic geniculate form. This species occurs in the same environment, and belongs to the same paragenesis, as its dimorphs, brookite and anatase.

Commonly, long, needlelike rutile crystals pierce dolomite and calcite crystals, and are seen as inclusions in quartz. A few rare specimens show rutile in association with hingganite or monazite. In 1994, in the footwall of the talc structure, a few isolated, red crystals of the "sagenite" type of rutile (to 1 mm) were found with calcite in the chloritization zone (Favreau, 1994).

Schorl Na[Fe.sub.3.sup.3+][Al.sub.6](B[O.sub.3])3[[Si.sub.6][O.sub.18]](OH)[.sub.4]

Schorl, as poorly formed, millimeter-size crystals with vertical striations, is found embedded in the pegmatites of the footwall of the talc mineralization zone. Sharply terminated schorl crystals to several centimeters were found in 1998 in a pegmatitic zone about 100 meters to the west of the talc-chlorite structure.

Stellerite [Ca.sub.4]([Al.sub.8][Si.sub.28][O.sub.72])*28[H.sub.2]O

Morphologically similar to stilbite, stellerite forms white, rectangular, millimeter-size crystals in the dumps at the footwall of the talc-chlorite mineralization zone. It may be accompanied by quartz and epidote (Favreau, 1994). This mineral has thus far not been found in situ, and has only been identified visually.

Stibnite [Sb.sub.2][S.sub.3]

Stibnite comes from the footwall pegmatites of the talc-chlorite structure. A few specimens were reported at the end of 1985 and in the beginning of 1986; they show millimeter-size, striated acicular crystals, some of them bent, associated with calcite (Favreau, 1994).

The mineral was analyzed, but has not been found again since 1986.

Stilbite-Ca ([Ca.sub.0.5],K,Na)[.sub.9][[Al.sub.9][Si.sub.27][O.sub.72]]*28[H.sub.2]O

Stilbite is found as vitreous white, opaque to transparent, millimeter-size radial aggregates. Rare millimeter-size crystals, variably elongated, some of them lozenge-shaped, came from the hydrothermally altered zone near the contact with the talc-chlorite lens in the same environment as the scolecite and chabazite found in the footwall of the talc-chlorite deposit (Favreau, 1994). The identification was visual, and has not been analytically confirmed. The mineral has not been found since 1994.

Sulfur S

Sulfur results from the decomposition of pyrite in the hanging wall of the talc-chlorite mineralization zone. It forms lemon-yellow coatings to 1 cm across in microfissures, and as powdery films, and, more rarely, subhedral crystals to 1 mm.

Synchisite-(Ce) Ca(Ce,La)(C[O.sub.3])[.sub.2]F

Synchisite-(Ce) is chemically very similar to parisite-Ce, but probably more common in the deposit It occurs as orange to reddish brown prismatic crystals in the same environment as the parisite. The prisms are always truncated at both ends, enabling synchisite to be distinguished from parisite, which forms pointed crystals. The synchisite crystals are opaque to translucent, and rarely gemmy; the largest observed are 2.2 cm long and less than 1 cm thick (Boggild, 1953). Allanite is a common association and xenotime a very rare one; synchisite may also form syntaxic intergrowths with bastnasite (Parker and Brandenberger, 1946; Donnay et al., 1953).

[FIGURE 46 OMITTED]

[FIGURE 47 OMITTED]

Talc [Mg.sub.3][Si.sub.4][O.sub.10](OH)[.sub.2]

The talc of the Trimouns deposit is mainly amorphous and of varied colors, ranging from white through green to black. Eighteen varieties or quality grades are distinguished according to two criteria: chemical composition and whiteness.

For the mineralogist, crystalline talc is, of course, the most interesting form of the mineral. It is found in the hanging wall of the talc-chlorite mineralization zone in geodes and vugs in dolomite (some to 10 cm across), and in microfractures. It forms very thin, transparent, nacreous white to yellowish hexagonal sheets, fragile intergrown leaves, and clusters of spherules lining the vugs.

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Thorite (Th,U)Si[O.sub.4]

Very rarely, thorite is found as subhedral crystals in aggregates to several millimeters, black to brown with a greasy luster and an imperfect cleavage along {110}. Specimens of this description were collected in 1985 in the mica schist of the pegmatite zone in the footwall of the talc-chlorite structure.

Thortveitite (Sc,Y)[.sub.2][Si.sub.2][O.sub.7]

A handful of specimens of thortveitite was found in the hanging wall of the talc structure; the specimens came from the top part of the dolomite lenses, in the same environment as iimoriite, associated with banded dolomite. Some very rare, yellowish white, acicular thortveitite crystals to 1 mm, associated with pale dolomite, were collected from fissures in 1997, as were a few millimeter-size thortveitite crystals perched on crystals of bastnasite with calcite and clinochlore (Bianchi and Pilati, 1988; Schetelig, 1912, 1922).

The identification was made by G. C. Parodi of the Natural History Museum in Paris.

Titanite CaTiSi[O.sub.4]

Crystals of pink, opaque titanite, from a few millimeters to 3.5 cm in size, were found in the chlorite zone of the footwall of the talc structure in 1994.

Tornebohmite-(Ce) (Ce,La)[.sub.2]Al(Si[O.sub.4])[.sub.2](OH)

A few crystals of tornebohmite, dark green with a yellow play of color, from several millimeters to 1 cm in size and striated longitudinally, were found in the summer of 1997. They are associated with crystallized calcite in the immediate vicinity of the allanite/dissakisite occurrence in the hanging wall of the talc mineralization zone (Shen et al., 1982). The analyses and determinations were made by G. C. Parodi (University Paul Sabatier Toulouse).

Tremolite [square][Ca.sub.2][Mg.sub.5][Si.sub.8][O.sub.22](OH)[.sub.2]

Tremolite was reported as soon as the mining started in the 1900's, as whitish fibers up to several centimeters long, as well as a pseudomorph after talc.

The mineral has not been found in situ since the time of Lacroix (1896).

[FIGURE 52 OMITTED]

[FIGURE 53 OMITTED]

Trimounsite-(Y) [Y.sub.2][Ti.sub.2]Si[O.sub.9]

Trimounsite-(Y), named after the Trimouns locality by Piret et al. (1990), occurs as brown acicular prisms and pale brown, translucent to slightly smoky, flattened rod-like crystals with longitudinal striations. It is found in vugs to several centimeters across, in gray and white dolomite in the hanging wall of the talc structure.

The crystals are elongated parallel to [001], and display the forms {110}, {130}, {211}, {121} and {011}. Forms {110} and {130} alternate, and the resultant faces appear striated. Trimounsite-(Y) crystals reach only 1 mm long and a few microns thick, and are easily confused with allanite. The only distinction is that allanite crystals have a characteristic termination that is oblique to the prism. Trimounsite-(Y) is monoclinic with a unit cell of a = 12.299, b = 11.120, c = 4.858. Also to be noted is its intense blue luminescence under the microprobe beam.

Since the collection of a very few specimens in 1989, all searches for further samples have been unfruitful.

Xenotime-(Y) YP[O.sub.4]

Honey-yellow to brown, translucent crystals of xenotime to several millimeters have been found in the hanging wall of the talc structure. Most are isolated, doubly terminated crystals and some are twinned. Clusters of crystals are found rarely in small vugs of crystallized dolomite and calcite. Isotopic dating gives an average age 110 Ma (De Parseval, 1992), the same as for the monazite (see above).

[FIGURE 54 OMITTED]

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Zircon ZrSi[O.sub.4]

A few brown, vitreous crystals of zircon to several millimeters in size, have been found in the pegmatite zone close to the hanging wall of the talc-chlorite structure.

CONCLUSION

The identification of certain rare earth element-bearing minerals from Trimouns, both carbonates and silicates, proved to be very difficult, because the minerals are chemically complex. Only by employing a variety of analytical methods including X-ray diffraction, scanning electron microscopy and electron probe microanalysis, has it been possible to identify them.

Today, the zone containing the rare earch minerals in the hanging wall of the talc-chlorite structure is very nearly exhausted. This zone is, economically speaking, a barren part of the deposit, and nearly all of it now has been stripped, dumped as spoil and covered with earth. In fact, under current French environmental law, the area must now be reclaimed for sustainable development, and the present dump material replanted with trees (Hoffler et al., 2000).

The Trimouns quarry has already acquired an international mineralogical reputation, both for its exotic species and for the quality of its crystals. It will probably figure among the great classic localities of tomorrow, comparable to the fabulous Mont Saint Hilaire deposit in Canada (although not equalling it in the diversity of species found).

Although only very small numbers of specimens of some of its rare minerals, e.g. trimounsite and gatelite, have been discovered, the Trimouns deposit may yet provide more surprises, most likely in the quarry's northern extension, where overburden is now being stripped away. Systematic exploration of the Trimouns area may well locate additional interesting mineral occurrences. Detailed quantitative analyses should enable other unusual species, perhaps including new ones, to be found, as well as illuminating the origin of these species.

All of the pictured minerals are from the collection of F. Marty, except as noted.
Table 1. The Rare Earths Elements.

21 Sc (Scandium) * Parodi 1998  64 Gd (Gadolinium)*
39 Y (Yttrium) *                65 Tb (Terbium)
57 La (Lanthanum) *             66 Dy (Dysprosium)*
58 Ce (Cerium) *                67 Ho (Holmium)
59 Pr (Praseodymum) *           68 Er (Erbium)
60 Nd (Neodymum) *              69 Tm (Thulium)
61 Pm (Promethium)              70 Yb (Ytterbium)
62 Sm (Samarium) *              71 Lu (Lutetium)
63 Eu (Europium)

* present at Trimouns (Moelo et al., 1974)

Table 2. Rare earth minerals found at Trimouns.

Carbonates          Oxides
  Bastnasite-(Ce)     Allanite-(Ce)
  Parisite-(Ce)       Dissakisite-(Ce)
  Synchisite-(Ce)     Gatelite-(Ce)
                      Hingganite-(Y)
                      Iimoriite-(Y)
Phosphates            Thortveitite-(Sc)
  Monazite (Ce)       Tornebohmite-(Ce)
  Xenotime-(Y)        Trimounsite-(Y)
Silicates
  Aeschynite (Y)

Table 3. Minerals found at Trimouns and their abundances.

Native elements
  Graphite ++++           Albite ++
  Sulphur +               Allanite-(Ce) +++
Sulphides                 Almandin ++
  Arsenopyrite +          Chabasite +++
  Chalcopyrite +          Chlorite ++
  Galena +                Clinochlore (Sheridanite) +++
  Pyrite ++++             Clinozoizite +
  Pyrrhotite +            Diopside +
  Stibnite +              Dissakisite-(Ce) +++
Oxides                    Epidote ++
  Aeschynite-(Y) ++       Gatelite-(Ce) + (type locality)
  Anatase +               Hellandite-(Y) +
  Brookite +              Hingganite-(Y) ++
  Cassiterite ++          Iimoriite-(Y) ++
  Goethite +              Microcline ++
  Hematite +            Silicates
  Limonite +++            Muscovite +++
  Niobo-Tantalate +       Natrolite ++
  Quartz +++              Palygorskite ++
  Rutile ++               Phlogopite +++
Halides                   Schorl (tourmaline) ++
  Halite +                Stellerite +
Carbonates                Talc ++++
  Aragonite ++            Thorite +
  Bastnasite-(Ce) +++     Thortveitite-(Sc) +
  Calcite ++++            Titanite (sphene) ++
  Dolomite ++++           Tornebohmite-(Ce) +
  Malachite ++            Tremolite ++
  Parisite-(Ce) ++        Trimounsite(Y) +
  Synchisite-(Ce) +++       (type locality)
Sulphates                 Zircon ++
  Gypsum ++
Phosphates
  Fluorapatite +
  Monazite-(Ce) ++
  Xenotime-(Y) ++

+ very rare
++ rare
+++ common
++++ abundant


ACKNOWLEDGMENTS

First of all, we acknowledge the collaboration of Mr. Laurent Gautron regarding the history and bibliography of the deposit and its minerals, likewise the Bureau de Recherches Geologiques et Minieres (BRGM), Orleans. We also should like to thank Talc de Luzenac, and in particular Mme. Vinandi and Mr. Hoffler, for their kind authorization. Mr. Gian Carlo Parodi of the Natural History Museum of Paris provided an invaluable help in SEM and X-ray diffraction analyses. Mr. Michel Deliens of the Royal Institute of Natural Science, Belgium, is thanked for trimounsite determination.

We should like to thank also MM. Eric Marcoux, Course Supervisor, Orleans University, and Jean Breton, BRGM, for SEM analyses; Francois Fontan for Debeye Scherrer analyses; and de Parseval and others from the Mineralogy and Crystallography laboratory of the Paul Sabatier University, Toulouse. Mr. Julien Pinato is thanked for his 1999 Masters thesis on which the regional-scale tectonics and geology was based.

We should not forget Association Francaise de Micromineralogie (A.F.M) and MM. Bernadi, Gatel, Favreau, Ronsin, Pecorini, Biglia, Jassereau, Audoui, Auriol-Ferre--collectors of microminerals--for their contribution to this work.

We thank Mr. Jean-Claude Boulliard, conservativer at the University P. and M. Curie in Paris for his good advice.

The photographs which illustrate this paper are from Mr. Robert Vernet (excellent stereographic color slides of most of the samples), Mr. Louis-Dominique Bayle (exceptional photos of the minerals), Mr. Jeffrey Scovil (extraordinary photos of the minerals and crystals), Miss Nadine Massarotto, and Talcs de Luzenac (photographs of the site).

Sir Patrick Skipwith translated the text from the French, and Thomas Moore and Dr. Wendell Wilson of the Mineralogical Record refined and edited the translation.

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