Printer Friendly

Minerals of the Seravezza marble, Tuscany, Italy.

The Seravezza marble quarries in Tuscany are as interesting for their microminerals as the more famous Carrara marble quarries 20 km to the northeast. The mix of species is somewhat different, however, including such minerals as boulangerite, zinkenite, guettardite, robinsonite, baumhauerite, bindheimite and bournonite which are rarer or entirely absent at Carrara.

INTRODUCTION

The Seravezza quarrying district is located about 20 km southwest of Carrara, the famous marble deposit where over 70 mineral species have been found (Franzini et al., 1987; Orlandi and Del Chiaro, 1989).

The cavity minerals of the Seravezza marble have received much less scientific attention; actually, just two papers, concerning guettardite and robinsonite from Seravezza, have been published (Bracci et al., 1980; Franzini, Orlandi and Pasero, 1992). Our purpose here is to describe the geology of this interesting locality and the 51 mineral species which have been identified thus far (Table 1).

LOCATION

The town of Seravezza is located in Versilia, a district in the Tuscan province of Lucca, about 35 km north of Pisa and 20 km southwest of Carrara [ILLUSTRATION FOR FIGURE 1 OMITTED]. The marble quarries are on the eastern slopes of Monte Trambiserra (Pitone area) and on the southwestern slopes of Monte Ornato (Ceragiola and Costa areas).

The Pitone area hosts two quarries: a larger one, the Biagi quarry, and, further south, the smaller Tessa quarry. Quarrying activities there came to an end in 1984; only minor maintenance operations have taken place since then. The Costa area hosts several quarries, only one of which is active at the present time. The Ceragiola area includes the active Tognetti quarry, and the Bigi and Agostini quarries, which ceased operations in 1982-1983.

GEOLOGY

The Seravezza marbles crop out at the southwestern rim of the tectonic "window" of the Apuan Alps; they are part of an epizonal metamorphic complex originating from a Tertiary Tuscan sedimentary sequence. The Seravezza marbles are located along the southern boundary between the Massa Unit and the phyllitic Paleozoic basement, which hosts the main sulfide mineralization of the Apuan Alps (Carmignani and Giglia, 1975).

Other extensive marble outcrops occur in the northeastern and central part of the apuan metamorphic complex (Arni, Monte Altissimo, Isola Santa and Resceto). A few mineral specimens from this general area are beginning to appear and have been submitted by field collectors for identification; it is likely, therefore, that interesting finds will be reported in the future.

CAVITY FORMATION

The minerals of the Seravezza marbles, like those of Carrara, occur in cavities generated by the deformation process during Tertiary metamorphism (Carmignani and Kligfield, 1990, and references therein). While the Carrara cavities are often tube-like with a diameter of about 10 cm and length up to several meters, the Seravezza cavities have an elongated, sometimes s-shaped cross-section only a few millimeters to a few centimeters wide and 10 to 30 cm high; the length can reach several meters [ILLUSTRATION FOR FIGURE 2 OMITTED].

These cavities lie en echelon on definite horizons related to the schistosity surface of the first metamorphic phase, which was refolded during the second metamorphic deformation. A second schistosity surface associated with the folds above and lying at a small inclination can sometimes be seen. The elongated cross-sections of the cavities where mineralization occurs are emplaced at a high angle with respect to both the first and the second schistosity surfaces.

A model for the formation of the cavities is illustrated in Figure 4, which suggests that tension gashes have been produced by shearing stresses concentrated on certain horizons.

The structural data show that these phenomena are related to the late tectonic evolution of the Apuan metamorphic complex, and that they are consistent with the post-collisional processes which, in this area, appear as a southwest-dipping extensional shear zone and ductile extensional faults (Carmignani and Kligfield, 1990).

The deformation process which opened the cavities brought about a pressure gradient around the cavity area, which activated the circulation of mineralizing solutions in the cavities. It is likely that at least part of the solutions were not of external origin, but originated from within the marble itself.

MINERALOGY

The first species deposited were: quartz (not common here), galena, pyrite, sphalerite, enargite, colusite and fluorite. The lead sulfosalts appear to have been deposited in a later phase, while smythite, marcasite, dolomite, gypsum and "wad" were deposited last.

Secondary minerals such as cerussite, hydrozincite, smith-sonite, wulfenite, mimetite, etc. were formed much more recently during alteration processes caused by the circulation of surface water.

All the species described in this article were identified by X-ray diffraction methods. The minute dimensions of the crystals required, in most cases, the use of the Gandolfi camera to generate powder diffraction patterns and the Weissenberg camera for single-crystal diffraction patterns.

The chemical analyses of sulfides and sulfosalts were carried out on an ARLSEM-Q electron microprobe, using the following standards: natural galena for Pb and S; natural stibnite for Sb, natural chalcopyrite for Cu, metallic Cd for Cd and natural arsenopyrite for As and Fe.

The chemical formulas of the minerals listed below and on Table 1 are from Fleischer and Mandarino (1991). Table 1 lists the minerals reported from Seravezza, arranged according to Strunz's Mineralogische Tabellen (1978).

Adamite [Zn.sub.2](As[O.sub.4]) (OH)

Minute apple-green crystals of adamite in globular aggregates up to 1 mm have been found only once, at the Costa quarry.

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

Albite occurs sparingly in various quarries as clear tabular crystals.

Anglesite PbS[O.sub.4]

Just one crystal of anglesite, smaller than 1 mm, has been found near a fragment of altered galena.

Arsenopyrite FeAsS

Rare prismatic crystals of arsenopyrite with rhombic cross-section occur elongated on the c-axis, and are normally smaller than 1 mm. The color is pale lead-gray, sometimes tarnishing yellow. All known specimens were collected at the Costa quarry.

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

Rare azurite is normally associated with malachite. A few fairly showy microcrystal specimens of azurite up to 1 mm were collected at the Tognetti quarry.

Barite BaS[O.sub.4]

Milky white, tabular crystals of barite to 1 or 2 cm occur sparingly in all of the Seravezza quarries.

Baumhauerite (?) [Pb.sub.3][As.sub.4][S.sub.9]

A black, metallic, acicular crystal removed from a specimen Collected at the Pitone quarry was found probably to be baumhauerite. Two chemical analyses and a Gandolfi camera powder X-ray diffraction pattern were obtained. Unfortunately the crystal is no longer available and further examination of the same specimen, containing both boulangerite and guettardite crystals, did not reveal any more baumhauerite.

The microprobe chemical analyses (Giananti, 1987, specimens 8a and 8b) gave results (shown in Table 2, samples 1 and 2) which are very close to those reported by Jambor (1967) for antimonian baumhauerite from Madoc, Ontario.

Bindheimite [Pb.sub.2][Sb.sub.2][O.sub.6](O,OH)

Like duftite, bindheimite has been found only in one specimen, as white earthy pseudomorphs after acicular crystals of lead sulphoantimonides.

Boulangerite [Pb.sub.5][Sb.sub.4][S.sub.11]

Boulangerite is common in all the Seravezza quarries, as acicular, extremely flexible crystals up to a few centimeters. The crystals are grouped in irregular or matted aggregates which are very dark gray, almost black, with a bright metallic luster. Some crystals may be thicker, stiffer and more brittle, and do not show the striations which are typical of zinkenite. Curved or curled crystals forming small rings and cylinders are not uncommon.

Microprobe chemical analysis (Giananti, 1987, specimen 19) gave the results shown in Table 2 (sample 6).

Bournonite PbCuSb[S.sub.3]

Dark lead-gray, shiny metallic crystals of bournonite up to 2-3 mm, normally tabular and twinned, are uncommon. Square bipyramidal crystals have also been found, associated with minute crystals of tetrahedrite.

The chemical analysis of one crystal (Dalena, 1978) is shown in Table 2 (sample 3).

Calcite CaC[O.sub.3]

Calcite crystals up to a few millimeters, but occasionally larger than 1 cm, line all the marble cavities. The crystals nearly always have a slightly elongated rhombohedral habit; the faces are often striated in a direction parallel to the crystal edges. Particularly interesting are some perfectly clear, twinned rhombohedral crystals which simulate a trigonal bipyramid.

Celestine SrS[O.sub.4]

Transparent or white prismatic celestine crystals up to 1 mm, individually and in crystal sprays, are uncommon, but may be found more often in the Ceragiola quarries.

[TABULAR DATA FOR TABLE 1 OMITTED]

[TABULAR DATA FOR TABLE 2 OMITTED]

Cerussite PbC[O.sub.3]

Cerussite occurs rarely in transparent, tabular crystals up to 1 mm on altered galena. It is common as gray, glassy granules, often enclosing relict fragments of unaltered galena.

Chalcopyrite CuFe[S.sub.2]

Chalcopyrite has very rarely been found as yellow, metallic, bisphenoidal crystals smaller than 1 mm.

Colusite [Cu.sub.26][V.sub.2][(As,Sn,Sb).sub.6][S.sub.32]

A few specimens of colusite crystals up to 4 mm, with typical tetrahedral habit, bronze-yellow color and metallic luster, have been found in the Costa and Pitone quarries. No chemical data are available on this species from Seravezza; in the Carrara marble both As-rich and Sn-rich members have been found (Orlandi et al., 1981).

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

Dolomite is very common at Seravezza as white, isolated rhombohedral crystals with pearly luster, often in the typical saddle-like aggregates. Crystals are up to 1 cm long, sometimes with greenish or pinkish tinges.

Duftite PbCu(As[O.sub.4])(OH)

Apple-green, earthy duftite associated with bindheimite has been found in a single specimen from the Tognetti quarry. This mineral appears to be the alteration pseudomorph of a sulfosalt in acicular crystals to several millimeters in length.

Enargite [Cu.sub.3]As[S.sub.4]

Although uncommon, fine specimens of enargite, as tabular, pitch-black, 4-5 mm crystals with bright metallic luster, have been collected at the Pitone quarries. Enargite is frequently associated with stibnite, wurtzite, sphalerite and acicular crystals of lead sulfoantimonides.

Fluorite Ca[F.sub.2]

Fluorite occurs in small, colorless or, less frequently, purple cubes. Rather uncommon in the Seravezza area, it is rare in the Pitone quarries, but more common in the Ceragiola quarries.

Galena PbS

Galena is a fairly common mineral at Seravezza. The crystals are cubic, octahedral or cuboctahedral, and often twinned. Sometimes the crystals are deformed or flattened on the three-fold axis to yield an hexagonal outline, similar to those from Carrara (Franzini et al., 1987).

Guettardite Pb[(Sb,As).sub.2][S.sub.4]

Guettardite occurs as prismatic to acicular or sometimes tabular crystals. The length-to-diameter ratio of the crystals is not as large as for boulangerite and zinkenite. The black color and metallic luster aid in visual identification of this mineral from boulangerite and zinkenite, which are lead-gray. Some rare, terminated crystals are tabular, with a rectangular cross section, showing the pseudo-orthorhombic symmetry of the species.

Guettardite is rare but has been collected both in the Ceragiola and in the Pitone quarries. Chemical analyses (Giananti, 1987, specimens 4 and 9) gave the results shown on Table 2, samples 4 and 5. The specimens above have been identified by X-ray diffraction patterns both on single crystals (Weisseberg and Buerger methods) and on Gandolfi camera.

Gypsum CaS[O.sub.4][center dot]2[H.sub.2]O

Clear crystals of gypsum up to 1 cm or more are common in all quarries.

Hydrozincite [Zn.sub.5][(C[O.sub.3]).sub.2][(OH).sub.6]

Rare hydrozincite is found in small, earthy white globules up to 3 mm in size, as an alteration product of sphalerite.

Jordanire [Pb.sub.14][(As,Sb).sub.6][S.sub.23]

Jordanite occurs as lustrous, lead-gray crystals up to 1 cm, with a pseudohexagonal, "bipyramidal" stepped habit. A rare species, it has been found more frequently in the Ceragiola quarries. Qualitative EDS analyses have shown a very low Sb content, indicating a chemical composition very close to the As end-member of the jordanite-geocronite series.

Luzonite [Cu.sub.3]As[S.sub.4] / Famatinite [Cu.sub.3]Sb[S.sub.4]

The identification of luzonite/famatinite from Seravezza is based on Gandolfi camera powder X-ray diffraction patterns; no precise chemical data are available, so that attribution to either luzonite or famatinite is not possible at this time. The crystals, up to 1 mm in size, have a bisphenoidal habit, metallic luster and a bronze color, sometimes with a purple tinge.

The few specimens recorded have been found in the Ceragiola and Pitone areas; it is normally associated with zinkenite, stibnite and bournonite.

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

Rare in coatings, crusts and globules up to 1 mm, malachite occurs scattered near altered copper sulfides and sulfosalts.

Marcasite Fe[S.sub.2]

Marcasite is very rare, occurring as poorly formed, very brittle tabular metallic crystals; it has been found in association with zinkenite in the Ceragiola quarries.

Millerite NiS

Just one millerite specimen has been found at Seravezza; it consists of a spray of acicular crystals 3 to 4 mm long, showing the typical brassy yellow color and metallic luster.

Mimetite [Pb.sub.5][(As[O.sub.4]).sub.3]Cl

Sprays of milk-white crystals of mimetite up to 0.1 mm occur occasionally on partly altered zinkenite crystals. Also, yellow prismatic crystals have been found rarely.

Orpiment [As.sub.2][S.sub.3]

Acicular crystals of orpiment up to 1 mm, with the typical yellow color, are found at the same localities as realgar.

Orthoclase ("adularia") KAl[Si.sub.3][O.sub.8]

The "adularia" variety of orthoclase has been found rarely at the Pitone quarries, as milky crystals up to almost 1 cm.

Pyrite Fe[S.sub.2]

Pyrite is the most common sulfide at Seravezza. It occurs as pyritohedral and, more rarely, octahedral and cubic crystals up to 1 cm.

Quartz Si[O.sub.2]

Quartz is almost completely absent from the Pitone quarries and rather uncommon in the Ceragiola quarries, where it occurs (mostly in the Tognetti quarry) in crystals seldom larger than 1 cm.

Realgar AsS

Realgar is rare at Seravezza. Bright red, prismatic crystals up to 1 mm occur rarely in the Pitone and Ceragiola areas, and particularly in the Tognetti quarry.

"Red acicular sulfoarsenide"

This mineral, as yet unidentified, has an X-ray powder diffraction pattern very similar to that of robinsonite. A qualitative EDS analysis has shown the presence of Pb, As and S only. No single crystals suitable for a crystallographic study have been found. The brick-red acicular crystals are fairly widespread in several of the quarries, and are normally associated with jordanite, robinsonite and yellow sphalerite.

Robinsonite [Pb.sub.4][Sb.sub.6][S.sub.13]

Robinsonite, a lead sulfosalt, shows a prismatic to acicular habit, with a length-to-diameter ratio similar to that of guettardite, and with a similar, or even brighter, metallic luster. The elongated prism faces of robinsonite are not striated; often the crystals are distinctly terminated by small shiny facets.

Robinsonite is rare; it has been found at the Pitone quarries, often with yellow sphalerite and, sometimes, with gypsum (Franzini, Orlandi and Pasero, 1992).

Rosasite [(Cu,Zn).sub.2](C[O.sub.3])[(OH).sub.2]

Rosasite has been observed with malachite and azurite as an alteration product of sulfides and sulfosalts, forming coatings, crusts and, sometimes, globular aggregates of tiny blue crystals associated with bindheimite and duftite.

Rutile Ti[O.sub.2]

Reddish, prismatic crystals of rutile up to a few millimeters have been found rarely at the Pitone quarries.

Semseyite [Pb.sub.9][Sb.sub.8][S.sub.21]

A few semseyite crystals about 1 mm in size have been found in the Ceragiola area. These crystals show a pitch-black color and metallic luster similar to that of enargite, but they are lenticular in habit and curved into a helix-shape. A microprobe chemical analysis yielded the composition shown in Table 2 (sample 7).

Smithsonite ZnC[O.sub.3]

Smithsonite is very rare at Seravezza; it occurs in brownish to yellow rhombohedral crystals, smaller than 1 mm, sometimes with hydrozincite, on altered, skeletal sphalerite crystals.

Smythite [(Fe,Ni).sub.9][S.sub.11]

Very thin (0.01 mm), tabular, bronze-colored smythite crystals up to 2 mm have been found at the Ceragiola quarries. Normally the crystals lie on calcite crystals and do not penetrate them, thus indicating very late deposition in the cavities.

Sphalerite (Zn,Fe)S

After pyrite, sphalerite is the most common sulfide at Seravezza and has been found in all quarries. The crystals, up to 5 mm, are often ruby-red and complex in form; more rarely they can be tetrahedral and yellow in color. The red variety is associated with galena, geocronite and bournonite; the yellow variety with colusite, wurtzite and robinsonite.

Microprobe chemical analyses of an orange-red crystal and of a dark brown crystal gave the results shown in Table 2 (samples 8 and 9). This analysis suggests that the darker color is caused by a higher iron content.

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

Stibnite occurs in metallic, gray-black crystals, either with a stout prismatic habit or with a very thin acicular habit. The larger crystals, up to 3 mm in length, are prismatic with shiny, very seldom striated faces. Sometimes the prism is terminated by small, triangular, orthorhombic dipyramid faces giving the crystal a typical "bell tower" habit. The acicular crystals are often grouped in sheaf-like aggregates. Stibnite is sometimes associated with wurtzite and enargite. Moderately rare at the Pitone quarries, it is rather rare in the other Seravezza quarries.

Strontianite SrC[O.sub.3]

White, acicular crystals of strontianite to 2 mm, forming sprays, spherules and sheaf-like aggregates, are common at the Ceragiola quarries, but are rare elsewhere.

An accurate determination of the interplanar distance d(132) by X-ray powder diffraction method gave the result of 1.982(2) [Angstrom]. This value indicates a calcium-rich variety of strontianite, containing about 15 mole % CaC[O.sub.3] (Speer, 1983).

Sulfur S

Sulfur is fairly common in all of the Seravezza quarries, especially in the Tognetti quarry and in the Pitone area. The crystals, seldom larger than 4 mm, are normally rounded as if they had been gently melted or redissolved after deposition. This feature is common also to the sulfur of the Carrara cavities. Transparent, sharp, bipyramidal crystals with shiny faces are rare.

Sulvanite [Cu.sub.3]V[S.sub.4]

Just one specimen of sulvanite has been reported from the Ceragiola area, as cubic crystals of about 1 mm, black, with a shiny metallic luster, and occurring in association with yellow sphalerite.

Tetrahedrite [(Cu,Fe).sub.12][Sb.sub.4][S.sub.13]

Tetrahedrite is uncommon at Seravezza, but equally distributed in the different quarries. The crystals, up to a few millimeters in size, often show a tetrahedral habit, but very complex crystals with many different facets and an almost rounded habit have been found. An EDS qualitative chemical analysis has shown an As:Sb ratio of about 1:10, with significant Fe and Zn.

"Wad"

The general term "wad," meaning undetermined manganese oxides, can be assigned to brownish, earthy globules up to 1 mm in diameter, found sparingly in the Ceragiola area; the qualitative EDS analysis has shown Mn to be the dominant cation in this mineral.

Wulfenite PbMo[O.sub.4]

Extremely rare at Seravezza, wulfenite has been found only once, at the Tognetti quarry, with other alteration products of galena as yellow tabular crystals less than a millimeter across.

Wurtzite (Zn,Fe)S

Wurtzite is moderately rare at the Pitone quarry, and very rare elsewhere at Seravezza. The crystals, which rarely exceed 2 mm in length, show the typical hexagonal pyramidal habit, sometimes flattened on the basal pinacoid. The most common color is red, but brown crystals and honey-yellow crystals have also been found. Microprobe chemical analyses of two crystals yielded the results in Table 2 (samples 10 and 11).

Zinkenite [Pb.sub.9][Sb.sub.22][S.sub.42]

Zinkenite is uncommon in all the Seravezza quarries. The crystals are acicular, with a cross-section larger than that of the boulangerite crystals; typical, very distinctive longitudinal striations give the crystals as fasciculated aspect. The color is lead-gray, paler than that of boulangerite. Sometimes zinkenite has an alteration patina dulling its typical metallic luster.

This species has been identified by single-crystal Weissenberg camera diffraction analysis. The cell has a pseudohexagonal symmetry with the following parameters: a = 44.2(1); c = 8.60(5) [Angstrom].

COMPARISON OF SERAVEZZA AND CARRARA

The Carrara and the Seravezza marble deposits, although similar in nature and origin, are rather different with respect to mineral association and relative abundance of the various species. At Carrara, the cavity minerals occur sparingly, in well-formed, individual crystals and crystal groups. At Seravezza, the mineralization may also occur as epithermal vein formations including the association of several sulfides (pyrite, sphalerite, galena) and sulfosalts (boulangerite, zinkenite, guettardite, etc.) which sometimes completely fill the marble clefts.
Table 3. Relative rarity of the Carrara and Seravezza minerals.


Mineral            Carrara(1)     Seravezza


Adamite             vr                vr
Albite              vc                 r
Anatase              r                 -
Anglesite            -                vr
Anhydrite            o                 -
Aragonite           vr                 -
Arsenopyrite        uv                 r
Aurichalcite         r                 -
Azurite              c                vc
Barite               r                 c
Baumhauerite         -                 u
Bindheimite          -                vr
Bornite             vr                 -
Boulangerite         r                 c
Bournonite           r                 c
Brookite            vr                 -
Calcite             vc                vc
Celestite           uc                 r
Cerussite           vr                 r
Chalcophyllite      vr                 -
Chalcopyrite        vr                 r
Chalcocite          vr                 -
Clinochlore         uc                 -
Colusite             r                vr
Connellite          vr                 -
Cornubite           vr                 -
Corellite           vr                 -
Cuprite             vr                 -
Dawsonite           vr                 -
Digenite            vr                 -
Dolomite            vc                vc
Duftite              -                vr
Enargite             c                 c
Fluorapatite         r                 -
Fluorite             c                 r
Galena              vc                 c
Gibbsite             r                 -
Guettardite          -                uc
Gypsum              vc                 c
Halloyisite         vr                 -
Hematite            vr                 -
Hemimorphite         r                 -
Hydrozincite        vr                vr
Jordanite            r                 r
Kersterite          vr                 -
Litiophorite         r                 -
Luzonite-
Famatinite           r                vr
Magnetite           uc                 -
Malachite           uc                 r
Marcasite           vr                vr
Millerite           -                  u
Mimetite            vr                 r
Muscovite           uc                 -
Nordstrandite       vr                 -
Orpiment            vr                 r
Orthoclase
(adularia)           c                 r
Pyrite              vc                 c
Quartz              vc                 r
Realgar             vr                 r
"Red acicular
sulfoarsenide"       -                 c
Robinsonite          -                 r
Rosasite            vr                vr
Rutile              c                 vr
Sellaite            u                  -
Semseyite           vr                vr
Smythite            vr                vr
Sphalerite           c                 c
Stibnite             r                 c
Stronzianite         r                 r
Sulphur              c                 c
Sulvanite           vr                vr
Tetrahedrite        vr                 r
Thorogummite        vr                 -
Uraninite           vr                 -
Vaesite              u                 -
Volborthite         vr                 -
"Wad"                -                 r
Wulfenite           vr                vr
Wurtzite             r                 r
Zinkenite           vr                 c


c = common, vc = very common, r = rare,


vr = very rare, u = uncertain, uc = uncommon,


o = only one specimen known


1 Franzini et al., 1992.


Concerning the various mineral species, firstly it should be noted that calcite in Seravezza and in Carrara occurs in very different habits, so that specimens can be readily assigned to one or the other locality by visual inspection. The calcite crystals from Seravezza have a very simple habit consisting of the most common rhombohedron; the faces are invariably marked by inverse hopper striations resulting from successive growth phases. The calcite crystals from the Carrara marble, on the other hand, have specular faces and complex habits in which the rhombohedron seldom predominates.

A second important difference concerns quartz crystals, which occur in most Carrara geodes and have been famous there for over a century for their beauty and perfection, but are very rare in the Seravezza geodes.

The relative frequency of the various other species at the two localities can be assessed by comparing Table 1 with the table for Carrara minerals (Franzini, Orlandi, Bracci and Dalena, 1992), and is summarized here in Table 3.

The significant presence of lead sulfoantimonides and arsenides (in particular guettardite, robinsonite, zinkenite and boulangerite) in the Seravezza marble is in contrast to their virtual non-existence in the Carrara marble. Since the cavities at both localities were formed during the same extensional post-collisional process, and can reasonably be-considered to be of the same age, this difference can perhaps be explained by a difference in the chemistry of the circulating fluids.

The mechanism of remobilization, dissolution and recrystallization in the immediate vicinity of the cavities has certainly played an important role in the genesis of the minerals of the Seravezza marble, as it has for the minerals of the Carrara marble (Franzini et al., 1987). In the Seravezza mineralization, however, the influx of elements from sources located outside the marble deposit, through large-scale fluid circulation, must also be postulated. At Seravezza, the mineralization is closely reminiscent, in various ways, of the neighboring sulfide and sulfosalts mineralizations in the underlying phyllic Hercynic basement (Bottino, Gallena, Santa Barbara and La Rocca mines); this fact suggests that a genetic relationships between these deposits is likely.

ACKNOWLEDGMENTS

The authors wish to thank the many mineral collectors who have been their constant and most valuable support in field research. The attention of collectors has been moving from the more showy quartz crystals to small, less obvious, sometimes rare minerals which may yield, after laboratory study, interesting information.

We thank, in particular, Messrs. Marco Baldi, Andrea Dini, Mario Galli, Giampiero Gramigni, Alessandro Lari and Sergio Mancini, who have supplied us with study material; Dr. Giancarlo Deri who loaned many of the specimens used for mineral photography in this article; Dr. Giovanna Vezzalini for the many electron microprobe analyses carried out at the Modena University; and Dr. Di Pisa for his revision of the structural geology aspects of the manuscript.

We would like to dedicate this work to our friend, the late Dr. Giancarlo Brizzi, who died tragically with his wife Massima on June 12, 1992. His enthusiasm and competence in the field of mineralogy has added a lot to our knowledge of many Italian localities, including Seravezza; he made available a number of the specimens used in this study.

BIBLIOGRAPHY

BRACCI, G., DALENA, D., ORLANDI, P., DUCHI, G., and VEZZALINI, G. (1980) Guettardite from Tuscany, Italy: a second occurrence. The Canadian Mineralogist, 18, 13-15.

CARMIGNANI, L., and GIGLIA, G. (1975) Apercue sur la geologie des Apuanes. Bulletin Societe Geologique Francoise, ser. 7, 17, 963-978.

CARMIGNANI, L., and KLIGFIELD, R. (1990) Crustal extension in the Northern Apennines: The transition from compression to extension in the Alpi Apuane core complex. Tectonics, 9, No. 6, 1275-1303.

DALENA, D. (1978) I minerali delle geodi della formazione marmifera apuana. Degree thesis, Faculty of Mathematical, Physical and Natural Sciences, University of Pisa.

FLEISCHER, M., and MANDARINO, J. A. (1991) Glossary of Mineral Species. Mineralogical Record, Tucson.

FRANZINI, M., ORLANDI, P., BRACCI, G., and DALENA, D. (1987) Minerals of the Carrara Marble. Mineralogical Record, 18, 263-296.

FRANZINI, M., ORLANDI, P., BRACCI, G., and DALENA, D. (1992) Die Mineralien des Marmors von Carrara. Mineralien Welt, 4-92, 16-46.

FRANZINI, M., ORLANDI, P., and PASERO, M. (1992) Morphological, chemical and structural study of robinsonite ([Pb.sub.4][Sb.sub.6][S.sub.13]) from Alpi Apuane, Italy. Acta vulcanologica, Marinelli Volume, 2, 231-235.

GIANANTI, R. (1987) I minerali del marmo di Seravezza. Degree Thesis, Faculty of Mathematical, Physical and Natural Sciences, University of Pisa.

JAMBOR, J. L. (1967) New lead sulfantimonides from Madoc, Ontario. Part 2 - Mineral descriptions. Canadian Mineralogist, 9, 192-213.

ORLANDI, P., MERLINO, S., DUCHI, G., and VEZZALINI, G. (1981) Colusite, a new occurrence and crystal chemistry. Canadian Mineralogist, 19, 423-427.

ORLANDI, P., and DEL CHIARO, L. (1989) Nuovi dati sui minerali delle geodi del marmo di Carrara. Atti Societa Toscana Scienze Naturali, Memorie, 96, 313-325.

SPEER, J. A. (1983) Crystal chemistry and phase relations of orthorhombic carbonates. In: Carbonates: Mineralogy and Chemistry, ed. R. J. Reeder (Mineralogical Society of America: Reviews in Mineralogy, 11), 145-190.

STRUNZ, H. (1978) Mineralogische Tabellen. Akademische Verlagsgesellschaft Geest & Portig K. G. Leipzig.
COPYRIGHT 1996 The Mineralogical, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1996 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Author:Orlandi, Paolo; Del Chiaro, Lorenzo; Pagano, Renato
Publication:The Mineralogical Record
Date:Jan 1, 1996
Words:4583
Previous Article:The Billie mine, Death Valley, California.
Next Article:Mineral collecting in the cyber age.
Topics:

Terms of use | Privacy policy | Copyright © 2018 Farlex, Inc. | Feedback | For webmasters