Printer Friendly

Caldbeck Fells.

INTRODUCTION

The Caldbeck Fells mining district is a loosely defined area covering some 25 square kilometers south of the village of Caldbeck in the northeastern corner of the English Lake District, about 12 km northeast of Keswick. Prior to changes in the county boundaries in 1974, the Caldbeck Fells were part of the ancient county of Cumberland, since absorbed into the new county of Cumbria (a change which accounts for old label and reference discrepancies).

For the most part, the Caldbeck Fells consist of rolling, treeless moors dissected by numerous watercourses running in steep-sided valleys (a "fell" is an upland pasture, moor or high plateau, and a "beck" is a creek; "Caldbeck" = "Cold Creek"). The valleys are known locally as "gills," and it was in these "gills" that most of the mineral veins worked by the early miners were found. The area is now part of the Lake District National Park, and both collecting and vehicular traffic are restricted there; however, it is a popular tourist area for hikers.

[ILLUSTRATION OMITTED]

The pyromorphite, plumbogummite, hemimorphite and mimetite from the Caldbeck Fells were, and remain, among the finest the world has ever seen. They made the names of mines at Roughton Gill, Red Gill and Dry Gill synonymous with fine mineral specimens. The Caldbeck Fells district contains a greater variety of mineral species than any other area of comparable size in Great Britain. Approximately 175 valid mineral species have been recorded from the metalliferous veins; a further 40 are known from the country rocks. There are about a dozen species from various mines in the area that represent only the second or third world occurrence and over 30 that were, when first recorded, new to Great Britain. The Golden Hugh level of the Silver Gill vein is the type locality for redgillite.

Members of the pyromorphite group that occur there include matt-heddleite, mimetite. pyromorphite, hedyphane, phosphohedyphane and vanadinite. The first three occur in excellent specimens; vana-dinite is found there very rarely, its occurrence only considered of importance because of the extreme scarcity of this species in Great Britain. Other species for which the area was a renowned source of collector specimens include plumbogummite, linarite, hemimorphite, caledonite, leadhillite, scheelite and apatite. The Greenbank collection is well known for its superb examples of linarite. plumbogummite and hemimorphite in particular.

HISTORY

The earliest record of mining in Caldbeck probably dates to 1331, when an order of King Edward III mentions one Robert de Barton, whom the king had appointed as keeper of a silver mine in "Minerdale and Silverbek" in Cumberland County. In 1537, a silver mine was reported to be operating in the parish by a Royal Commission sent to investigate the northern estates. In 1563, at the behest of the English Crown, copper deposits throughout England were investigated by mining experts from Germany. England turned to Germany not only for technical expertise--16th century German miners and smelters led the world--but also for capital. Shares in the new company were more or less equally divided between the Germans and the English, the latter including prominent government officials and members of the aristocracy. The situation looked very promising, both sides anticipating vigorous business and large returns. The result was a disaster. A vast investment program was initiated to open or reopen the Cumbrian mines and to set up a large administrative and processing complex near Keswick. Here the company built the biggest smelter in Europe and coordinated a large network of suppliers of fuel, food, transport and other necessities. In 1567 the first copper metal was produced, the process taking 18 weeks and 5 days from dressed ore to "perfect copper."

Most of the copper ore came from mines to the west of Keswick but the Caldbeck mines were also producing ore. Copper and argentiferous lead ores were raised; the latter, of value principally for its silver, was also used in the processing of copper ores from the other mines.

The smelting works were prodigiously expensive and much delay was caused by the complexity of the Cumbrian ores, which tested the Germans' expertise to the limits. Copper output never reached the first optimistic forecasts, and sales were disappointingly slow. The company also had to contend with many social and legal difficulties, but, although most of their problems were eventually resolved in the company's favor, the slow progress and continuing cash-flow problems eventually caused the English shareholders to reconsider their commitment. The huge operating deficit, compounded by serious economic problems at home, proved too much for the German shareholders, who withdrew completely in 1577, leaving the Company of Mines Royal in the hands of the English shareholders and those of the original German staff who chose to remain.

Chief among those Germans who remained with the company was Daniel Hochstetter, founder of a dynasty of master smelters and miners who worked the Cumberland mines for many years. From 1580 to 1597 the company leased the Cumberland mines to the Hochsletters and others, rather than bear the financial responsibilities of running the mines themselves. Improved methods and economies allowed the lessees to make a reasonable living after paying the company's rent. The position of the Caldbeck mines during this period is uncertain because complete records do not exist. The mines were reported as closed in 1581: "the rich lead mine at Caldbeck. w'ch holdeth good quality of silver, and hath cost the company great sommes of mony: Lieth now unwrought." In 1600 the mines were being cleaned out with a view to reopening, but the miners considered that they "have no hope of comfort in this work of Caudbeck, but think the cost. ... bestowed there utterly lost." Other Cumbrian mines, however, were certainly worked. The Hochstetters and their colleagues made a profit in their first lease but went on to lose money in subsequent leases. Such patterns of profit and loss were to be typical of workings on the Caldbeck Fells veins right up to the closure of the last lead mine at the end of the 19th century.

For most of the 17th century the stale of the Caldbeck mines is little known. It is certain that attempts were made to work them and that recommendations were made from time to time to drive new adits to dewater old levels, but little seems to have been done. Certainly, by the outbreak of the Civil War in 1642, all the Cumberland mines and the smelters at Keswick were at a standstill. Oliver Cromwell's army is usually blamed for the destruction of the mills and mines and the death or conscription of the miners, but there is little evidence to support this claim. It is likely that the mines were run down or even abandoned before this date and that financial or technical problems rather than violence were responsible for the collapse of the mining and smelting.

The Caldbeck mines were investigated by several people in the 1680's with a view to reopening them but nothing came of it. By this time technological improvements in mining and smelting were making many old prospects potentially economic and the repeal of the Mines Royal Act in 1693 (whereby the Crown lost its prerogative for mines yielding precious metals) stimulated private investment in metal mining. The newly formed Company of Royal Mines Copper leased the Caldbeck mines in 1692; ten years later this company merged with another Quaker-owned firm to form what was to become the London Lead Company. This company was still smelting lead from "Caudbeck" in 1702.

Records for the 18th century are fragmentary but suggest a substantial interest in the Caldbeck mines. In the early part of the century one Thomas Hillary was chief agent to lead mines throughout the district, and accounts for his workings from 1724 to 1726 survive. These workings may have continued at least until 1730, but thereafter nothing is known of workings in Caldbeck until 1785 when Joseph Scott was working a copper mine in Hay Gill (in the north of the district). Scott continued until at least 1792. By 1794 smelters had been built at Roughton Gill and Driggith. and by 1800 mining was probably in full swing throughout the district.

The period 1820 to 1860 saw the golden age of mining in the Caldbeck Fells. During these years almost all the metal deposits were tried, some with great success, and some mine owners made fortunes stripping rich ore from the deposits and then selling out. But, in general, those who lingered lived to regret it and the lives of most of the mines ended in recriminations and bankruptcy. Much expense was incurred in development work, something that had been ignored by previous owners intent on quick profits. These financial problems were compounded by the complexity of the ores (which even the most up-to-date and expensive milling equipment could not handle successfully), by difficulties with drainage, and by incompetent management. As the century wore on, ores became progressively leaner and more difficult to extract as the mines became deeper, and self-draining adits became uneconomic or impossible to sustain. The death blow came with the catastrophic slump in metal prices in the 1870s. The market was flooded with cheap ore, much of it from America, and the remaining Caldbeck mines were forced to close.

[ILLUSTRATION OMITTED]

By 1876 the last lead mine had been abandoned, its owners bankrupt. From that time hardly any lead or copper has been raised, except as an occasional by-product of working the rich barite deposits in the north of the Fells. The last of these, at Potts Gill, closed in 1966. The Carrock tungsten mine has been the only commercial operation since then, and that only an intermittent operation during the 1970s and early 1980s. It is unlikely that Caldbeck will see the return of miners in the foreseeable future.

For references and fuller descriptions of these and other mines see Minerals of the English Lake District: Caldbeck Fells (M. P. Cooper and C. J. Stanley, 1990), and "Famous mineral localities: Pyromorphite group minerals from the Caldbeck Fells, Cumbria, England" by the same authors (Mineralogical Record, vol. 22, pages 105-121, 1991).

GEOLOGY

Many authors attribute the variety of minerals encountered in this area to the variety of host rocks, and to some extent this is true, for a number of quite distinct mineralizing events have occurred. Apart from a minor concentration of ilmenite in the basal gabbro of the Carrock Fell Igneous Complex, the earliest mineralization (Lower Devonian) is that which forms the north-south veins cutting the greisenized Skiddaw Granite, the homfelsed slates, and the gabbros and granophyres of the Carrock Fell Igneous Complex. Predominantly this deposit is composed of quartz, wolframite, scheelite, apatite and arsenopyrite with minor amounts of bismuth, bismuth tellurides and sulfides, pyrrhotite, chalcopyrite and sphalerite; it formed from late-stage fluids derived from the granite.

The deposits of copper, lead and zinc are found almost entirely in veins formed along faults in the volcanic and plutonic rocks of the Eycott Group and the Carrock Fell Igneous Complex respectively. Most of the veins have a simple primary sulfide mineralogy dominated by galena, chalcopyrite and sphalerite with minor pyrite. Bournonite, native antimony and argentiferous tetrahedrite are common as microscopic inclusions in galena. The dominant gangue minerals are quartz and barite. Calcite is locally abundant in the Roughton Gill South vein and the Carrock tungsten veins but uncommon elsewhere in the Caldbeck Fells. Fluorite is very rare.

Isotopic evidence suggests that the main period of copper-lead-zinc mineralization occurred in Upper Devonian to Lower Carboniferous times (ca. 360-330 million years ago). The later barite mineralization of the area was assigned an Upper Carboniferous to Permian age (ca. 290-260 million years ago). The formation of the secondary minerals, for which the Caldbeck Fells are famous, resulted from a hydrothermal event 190-180 million years ago which altered the host rocks and the primary mineral assemblages.

MINES

Cooper and Stanley (1990) identify 15 mines in the Caldbeck Fells district, only the most important of which (from a collector standpoint) will be discussed here.

Brae Fell mine

The Brae Fell mine was worked from two short crosscuts (now caved) to an approximately north-northwest-trending vein, and the size of the associated dumps suggest, in local terms, a relatively extensive operation. The mine was last opened in the mid-1800s but this was merely a trial operation and nothing came of it.

Pyromorphite and cerussite are common in small amounts on the dumps, but the Brae Fell mine is distinctive for being only the second known locality for the relatively new species mattheddleite. Mattheddleite occurs as etched prisms and pinkish masses on lead-hillite and cerussite and as sharp prismatic crystals with pyramidal terminations encrusting lanarkite.

Brandy Gill mine

An east-west lead vein crosses Brandy Gill just over 500 meters upstream from the Carrock tungsten mine. Two levels in the west bank have been explored in this century and proved to be mostly barren, although the lower level does show some old sloping. The mine was operated sporadically until about 1873, but only a few tons of lead and copper ore were raised. J. G. Goodchild, of the Scottish Geological Survey, found wulfenite there in 1875 but the locality only really became of interest to collectors in the 1950s following the reporting of a suite of rare supergene minerals including bayldonite, duftite, beudantite, carminite, lindgrenite and stolzite (the first authenticated British occurrence). Duftite, bayldonite, beudantite, and carminite are occasionally seen as epimorphs after small mimetite crystals.

[ILLUSTRATION OMITTED]

Carrock mine

The Carrock mine is the only British deposit outside of southwestern England that has been worked commercially for tungsten. Located in Grainsgill at the foot of Brandy Gill, it exploits three main structures: the Smith, Harding and Emerson veins. It was only intermittently economic, notably during World War I. Its last period of operation was in the 1970s. The north-south tungsten-bearing veins, a well-known source of fine scheelite, apatite, rare crystallized bismuth, arsenopyrite and other minerals, are cut by east-west lead veins; interaction between the two mineralizations has resulted in the formation of some interesting supergene minerals. Vanadinite specimens attributed (probably incorrectly) to the Carrock mine in the Kingsbury collection at the Natural History Museum, London, show small short-prismatic crystals, zoned pale brown and cream.

[ILLUSTRATION OMITTED]

Driggith mine

The Driggith mine is little known to mineral collectors outside the United Kingdom but has produced some interesting and characteristic pyromorphite-mimetite specimens as well as a suite of unusual rarities. It exploits a continuation of the Roughton Gill South lode from levels in the Driggith Valley and from lower levels over the fell at Sandbeds.

Ore minerals in the Driggith-Sandbeds vein were predominantly galena, sphalerite and chalcopyrite in a gangue of quartz and barite. The intimate association of galena, sphalerite and barite, especially in the deeper levels of the mine, caused insurmountable problems for the gravity separators used for ore-dressing in the Victorian workings and was a major cause of the failure of the mine.

The earliest records of mining at Driggith are in documents from the early 18th century but information is scanty until the turn of the 19th century. The mine was profitably worked in the first decades of the century but thereafter, despite brief profitability in the 1850s, the mine was worked at a loss by successive operators, most of whom ended up bankrupt. The mine was effectively finished by 1874. Several attempts to rework it in this century for lead or barite were defeated by the dilapidated state of the workings or the problems of ore separation. The last operation was in 1948. Production statistics are incomplete but the mine produced at least 3,800 tons of lead ore from 1845 to 1907, yielding some 2,500 tons of lead and 40,000 ounces of silver. Small amounts of copper, zinc and barite were also raised.

[ILLUSTRATION OMITTED]

Mimetite occurs at the Driggith mine in small, rounded, greenish to khaki-colored crystals encrusting quartz. The mineral frequently contains a high proportion of phosphate and forms a continuous series with pyromorphite; many specimens are of intermediate composition. Considerable quantities of pyromorphite are reputed to have been raised from the upper levels of the Driggith mine. The mineral is still common in the outcrops of the vein, generally forming small (<5 mm), opaque, rounded or seed-like, green to khaki-colored crystals encrusting quartz. Many specimens are near the midpoint in composition between mimetite and pyromorphite. A very characteristic form first recorded from the outcrop in the 1940s consists of masses of coarsely fibrous pyromorphite with pitted reniform surfaces, indistinctly color-zoned in shades of greenish yellow to yellowish green.

Dry Gill mine

Although of little commercial significance, the Dry Gill mine is one of the most famous mineral localities in the world. Lead minerals consisting predominantly of phosphate-rich mimetite in barrel-shaped crystals ("campylite") in a gangue of quartz, barite and manganese oxides were deposited in an east-west-trending vein. Other minerals occur rarely, the most well-known being plumbogummite.

Although mimetite specimens from Dry Gill are known to have been collected at least as early as 1830 there is no record of commercial ore mining there until a lease was taken by Hugh Lee Pattison, inventor of a cupellation process for the desilvering of lead. Pattison began work in 1846, driving an adit on the vein where it crosses Dry Gill Beck near the foot of the gill. He raised a few hundred tons of "coloured lead ore" but gave up the work in the 1850s. The property was subsequently tried by various operators, none of whom had much success. The mine was last worked in 1869.

The finest mimetite specimens were collected in the 19th century but, although increasingly hard to find, some fine material has been obtained since, particularly in the 1970s through the efforts of the partnership of Ralph and Michael Sutcliffe, Lindsay and Patricia Greenbank, and Richard Barstow. In 1970, after years of searching, Lindsay and Mick finally found a means of entry through a collapsed shaft that led out to the top of the fell. They managed to keep this to themselves for some years by manufacturing a "lid" to cover the mine opening and changing the lock every weekend (to the frustration of rival collectors also wanting entry). Plans to mine on a larger scale had to be canceled when a formal licensing application to the mineral rights owners was turned down in 1973. However, the mine is notoriously unstable, cold and wet, and there have been a number of accidents involving collectors. No one has been critically injured but the incidents have highlighted the dangers of the old workings in the Caldbeck Fells.

[ILLUSTRATION OMITTED]

[ILLUSTRATION OMITTED]

The deposit consists almost exclusively of mimetite and pyromorphite in a gangue of quartz, barite and manganese oxides. The quantity and quality of mimetite found at the Dry Gill mine makes the occurrence one of the most important in the world for this species. Specimens of mimetite from Dry Gill in the collections of the Natural History Museum, London, date from 1830, but the occurrence was not referred to in the literature until an "arseniate of lead" was described from Caldbeck in Allan's Phillips's Mineralogy (1837) as "... aggregated in opake, orange-yellow coloured individuals, which consist each of three hexagonal prisms curved towards their terminations in a manner often beautifully symmetrical." This mate-rial is undoubtedly identical to what Breithaupt formally described and named "campylite" (from the Greek campylos, "barrel") as a new species in 1841. Robert Allan's collection contains several specimens of typical Dry Gill mine mimetite.

Although campylite was later discredited as a species (= phosphatian mimetite), the name lingers on among collectors as a useful descriptive term for the characteristic barrel-like habit of mimetite found at the Dry Gill mine. Pyromorphite crystals are generally in the range 5-10 mm but exceptionally have been found as large as 3 cm across and thickly coating matrix pieces to over 20 cm. Excellent stalactiform specimens (to over 5 cm long) were also found in the 19th century. The color varies from yellow to orange and, rarely, green. More recently collected campylite specimens are most commonly varying shades of brown. Color zoning and chemical zoning are common, brown campylite often being paler and sometimes yellow or orange within. Yellow acicular crystals, commonly found encrusting brown campylite or embedded in crusts of plumbogum-mite, are usually labeled mimetite but most, if not all, such crystals are actually pyromorphite. Mimetite also commonly occurs as tabular and short to long prismatic crystals and in globular masses.

[ILLUSTRATION OMITTED]

[ILLUSTRATION OMITTED]

Mexico mine

The Mexico mine is located adjacent to the Roughton Gill mine and exploits the eastward extension of the Roughton Gill South vein. It was begun in 1845, and three crosscuts were driven south to cut the vein. Promising shoots of pyromorphite and cerussite were found early on, in what the miners called "phosphate ground," regarded as an indicator of rich primary ore below. The crosscuts, a shaft and drifts parallel to the vein were all cut on the assumption that rich primary ores would be found when the vein was opened up. In fact the lode proved to be almost barren, and the heavy investment, largely made by the Caldbeck Fells Consolidated Lead and Copper Mining Company, was wasted. The mine was abandoned in 1868.

Pyromorphite is still the most abundant lead mineral to be found on the Mexico mine dumps. Characteristic of the locality are small bicolored (orange and green) crystals, most commonly found on the Low Level dumps in Todd Gill. Pyromorphite has also been found on these dumps, associated with pale smoke-brown plumbogummite or with small plates of wulfenite.

[ILLUSTRATION OMITTED]

The finest pyromorphite to be found in the Caldbeck Fells in the last few decades was extracted in the 1970s from an outcrop of the Roughton Gill South vein just west of the Mexico mine High level. The original find was made by the late Richard Barstow; further material was dug by later collectors. This occurrence yielded many fine cabinet specimens displaying oil-green prismatic crystals to over 2.5 cm in solid masses and on quartz matrix. Later finds included pale yellow-green prisms to 2 cm or so and bright green botryoidal encrustations on matrix. On occasion several habits and colors were found in the same cavity. The locality is now worked out and backfilled.

Mimetite from the Mexico mine was first mentioned by Greg and Lettsom (1858). Brown, rounded crystals similar to, but distinct from, Dry Gill "campylite" have been found on the dumps from the High Level.

Old Potts Gill mine

Workings in the head of Potts Gill date from about 1870 when attempts were made to work the outcrop of the prominent east-west veins for lead. Very little lead ore was found in the predominantly barite-filled vein but the latter mineral was worked from the outbreak of World War I. The mine closed in 1947.

The barite mined was almost all massive and very little material of specimen quality was found. The deposit is of interest primarily for a suite of rare copper and lead minerals reported from the dumps of the "Old No. 1 level" by Arthur Kingsbury and J. Hartley.

Red Gill mine

The Elizabethans are supposed to have worked the Red Gill mine but no specific records have survived. Workings in Red Gill are mentioned in early 18th century documents but thereafter there is nothing known of the locality until the 19th century. The best-documented operations are those of the Red Gill Mining Company, which leased the property in 1861. The company extended the Red Gill mine and opened several other prospects nearby, but recorded production was very small. The company went bankrupt in 1871, having raised no more than 28 tons of lead ore and 45 tons of copper ore. From that time there has been no commercial exploitation of the mine.

[ILLUSTRATION OMITTED]

[ILLUSTRATION OMITTED]

[ILLUSTRATION OMITTED]

The Red Gill vein runs northwest-southeast and was worked from several levels in the spur between Swinburn Gill and Red Gill. Principal ore minerals were chalcopyrite and galena, closely associated in a gangue of quartz and barite. Intense oxidation resulted in a remarkable assemblage of supergene lead and copper sulfates including fine specimens of linarite, caledonite and leadhillite. The best specimens of these species were found while the mine was working; very few have been found in this century.

Specimens of such rarities as macphersonite, queitite and matt-heddleite have been found recently on the otherwise almost barren dumps. In fact, the Red Gill mine has been the most productive locality in the district for recently collected specimens of matthed-dleite. It has been found as microcrystals with caledonite, leadhillite and susannite on quartz, and in cavities in etched galena with minute sprays of pale blue lanarkite. Its occurrence seems restricted to the interior of cavities in the veinstone.

Roughton Gill mine

Roughton Gill is assumed to have been the site of the principal Elizabethan workings at Caldbeck Fells, although its present name does not appear in documents as a mining site before the end of the 18th century. Some workings are, however, undoubtedly ancient, as hand-cut levels can still be found in the higher workings.

The mine exploited two large lodes known as the Silver Gill and the Roughton Gill lodes. The former was named after the valley to the west where it was once extensively and (legend has it) very profitably worked. These names have fallen somewhat into disuse, and the veins are now generally known to geologists and mineralogists as the Roughton Gill North and Roughton Gill South lodes respectively. This terminology leads to some confusion because these terms were used by the old miners to denote branches of the Roughton Gill vein proper.

The principal ore minerals at Roughton Gill were argentiferous galena and chalcopyrite with lesser, though occasionally valuable, amounts of pyromorphite, cerussite and malachite. The gangue was mostly hard quartz but, in an occurrence unusual in the Lake District, large quantities of calcite were associated with the richest shoot of ore in the Roughton Gill South vein. The ore deposits were apparently richest where gabbro formed one of the walls of the vein, this and other country rocks being intensively altered for a considerable distance from the lode.

The earliest trials and levels are found in the higher reaches of Roughton Gill where the outcrop of the strong Roughton Gill South vein was worked from opencuts and short drives on the lode. In later years crosscuts were driven lower down the gill. There has been no access to the mine in living memory and this, along with the almost complete absence of any contemporary mine plans, means that the full extent of the workings is now unknown.

From about 1820, fortunes were made by a succession of owners but by 1865, when the mine was leased to the ill-fated Caldbeck Fells Consolidated Lead and Copper Mining Company, the richest ores were gone and the mine was in decline. The construction of the most up-to-date ore milling equipment and an expensive attempt to find ore below the 90-fathom level on the Cornish principle by the use of an engine shaft failed to improve the output or add to the known reserves. The market crash in the price of lead in the 1870s brought the company to bankruptcy in 1876. The mine closed and, apart from some interest shown by the Cleator Iron Ore Company, which worked barite and limonite in the Caldbeck Fells. Roughton Gill was effectively finished as a metal mine.

[ILLUSTRATION OMITTED]

[ILLUSTRATION OMITTED]

[ILLUSTRATION OMITTED]

[ILLUSTRATION OMITTED]

[ILLUSTRATION OMITTED]

[ILLUSTRATION OMITTED]

[ILLUSTRATION OMITTED]

[ILLUSTRATION OMITTED]

Records of production in the early period are vague. Output from the Roughton Gill workings alone are not recorded before the 19th century: the production figures are complicated by changes in ownership and were often given in combination with other mines worked by the same operator. Peak annual production of dressed lead ore was some 650 tons in 1851. From 1845 (the start of official production records) to the close of operations in 1876 some 10,500 tons of lead ore were raised, yielding over 6,000 tons of lead and about 13,000 ounces of silver. The mine also produced over 1,300 tons of copper ore in the same period; and 39 tons of zinc ore are recorded for 1873-74.

[ILLUSTRATION OMITTED]

The Roughton Gill South vein contained one of the most remarkable deposits of pyromorphite on record; so much was collected from one area on the 60-fathom level that it became known as "the specimen stope." Unfortunately most specimens collected when the mine was working are accompanied by no details of their precise location within the mine.

The most characteristic Roughton Gill pyromorphite specimens exhibit tapering yellow-green to oil-green prisms (resembling spindles when doubly terminated), in solid masses and as encrustations on cavernous quartz; oil-green pyromorphite in association with small-blue plumbogummite is a hallmark of the locality. Prismatic crystals may reach over 2 cm long but are generally less than 1 cm. Solid masses to 20 cm across are known in collections but pyromorphite probably occurred in much larger masses in the vein. Stalactites are rare (only 19th-century specimens are known) and may be very attractive when coated with sparkling crystal faces. The full range of color encompasses shades of green (from oil-green to emerald-green), yellow, gray, white, brown and orange.

The most common associated species is quartz and the most characteristic (and highly prized) is plumbogummite, particularly when the latter is of a deep blue shade. Rarely, small pyromorphite crystals are seen embedded in crusts of blue botryoidal hemimorphite and very rarely pyromorphite is found associated with small rounded mottramite crystals. Pseudomorphs of pyromorphite after cerussite have been found, and plumbogummite forms epimorphs after small prisms of pyromorphite. The latter were first described in 1843 by Johann Reinhard Blum as hemimorphite ("kiesel-zinc") pseudomorphs after pyromorphite--a very common 19th-century error.

[ILLUSTRATION OMITTED]

As with most occurrences of minerals in the Caldbeck Fells, the finest specimens of pyromorphite at Roughton Gill were found in the 19th century. When the mines declined, the supply of fine pyromorphite rapidly tailed off; as early as 1875 the dealer Bryce M. Wright, Jr. lamented that pyromorphite, once "the most common of Cumberland minerals [was] now very scarce." Nevertheless, even as recently as the 1940s and 1950s, fine specimens could still be collected from the dumps; one can only surmise the quantity of specimen-grade material available 100 years ago! In the last 50 years the thorough reworking of the sites by dealers and collectors has stripped away almost all of the cabinet-quality material to be found in the old dumps.

Mimetite is not as common at Roughton Gill as pyromorphite but there is little hard data on the distribution of the two species there, and mimetite may be more widespread than is supposed. "Wax-yellow crystals, well defined" were noted from Roughton Gill by Greg and Lettsom in 1858. Some fine specimens exist in old collections.

An outcrop of the Roughton Gill South vein in the higher reaches of the gill has recently yielded some good specimens of matthed-dleite in minute needles with caledonite, lanarkite, leadhillite and hydrocerussite. An excellent example (since sold) was in the Green-bank collection. A very rare association is the sulfite scotlandite. this being only the third known locality.

Other Localities

Other workings in the area include the Hay Gill. Silver Gill, Bur-dell Gill, Wet Swine Gill, Sandbeds, and Nether Row Brow mines. Some smaller sites are mentioned in mineral descriptions: Short Grain and Ingray Gill are shallow valleys in the northwestern part of the Fells. Each contains several small prospects for lead or barile or both. These workings probably date from the mid-19th century and are of small extent and little economic consequence.

[ILLUSTRATION OMITTED]

Transcription of a Bryce Wright letter to the curator of the British Museum mentioning the linarite; it is dated November 6, 1843:

Sir,

When I was at the British Museum last Spring, with some blue cupreous sulfate of lead [linarite], you told me if I met with anything more I was to let you know. Beg leave to send you the following, if you have not already got them.

--A beautiful brown specimen of sulfate of lead [cerussite], size on opposite page.

--4 beautiful arsenophosphates of lead [mimetite/pyromorphite], about 2 1/2 by 3 1/2 inches, chrystals of which are in the box [of] pure red color.

If you have them not, & will be kind enough to send me word, they shall be sent with the prices annexed.

I am, Sir, your ob't servant,

Brice Wright

56 Renshaw Street, Liverpool
COPYRIGHT 2010 The Mineralogical, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2010 Gale, Cengage Learning. All rights reserved.

 
Article Details
Printer friendly Cite/link Email Feedback
Author:Cooper, Michael P.; Stanley, Chris J.
Publication:The Mineralogical Record
Geographic Code:4EUUK
Date:Jan 1, 2010
Words:5436
Previous Article:Localities.
Next Article:The Force Crag mine.
Topics:

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