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The Weardale mines.

INTRODUCTION

Excellent fluorite specimens have come from a number of mines in the Weardale region since mining began there in the 12th century. Fortunately for the collecting community, there was generally a tolerant attitude on the part of mining companies toward the collecting of specimens by miners in their off hours. In fact, the miners considered it their right, and one of the few perks of the job. Selling the attractive specimens (referred to as "bonnie bits" by the miners) to collectors and mineral dealers provided the miners with additional, much-needed income. Thus today one can see superb examples of Weardale fluorite in museums and private collections around the world. Adding to this bounty is the renewed interest in recent years in mining specifically for specimens, providing the modern collector with an opportunity to select from substantial lots of newly collected material.

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The information on the district presented here is taken largely from Fisher (2004, 2006, 2009), Fisher and Greenbank (2000, 2003), Cooper (1996), Dunham (1948), Green and Briscoe (2002), Symes and Young (2008) and various mineral show reports.

HISTORY

Mining in the Northern Pennines probably goes back to Roman times, but most evidence of such activity was obliterated by later activities. Early methods of mining included the digging of round, shallow open pits (called "bell pits") along the vein, and hydraulic stripping of overburden through the sudden release of dammed up water (called "hushing). Two major lead-mining companies dominated the area during the 18th century: the London Lead Company (which obtained its first leases in 1692) and the Beaumont Company (which started about the same time). These two companies finally shut down in 1882 and 1884 respectively, in response to the worldwide crash in the market price of lead.

Iron oxide deposits in many of the replacement orebodies and veins throughout the Weardale district were also mined; the first record of iron production dates to the 12th century when the Bishop of Durham took a lease on a mine near Rookhope to produce iron for the manufacture of plow blades. Iron mining in the district, primarily by the Weardale Iron Company, peaked in the last half of the 1800s; smelting furnaces operated in the villages of Stanhope, Tow Law and Wolsingham. By the early 20th century, however, all iron mining in the district had ceased.

By the late 1800s the modern steel-making industry had developed a need for fluorite as a flux, and this new market rejuvenated the Weardale mines, where formerly fluorite had been discarded on the dumps as waste. Witherite and barite also proved profitable, and thus the local mines were supported well into the 20th century. Commercial production of fluorite in the Weardale district was initiated in 1882 by the Weardale Lead Company. Most mines shut down in the early 1980s when the British steel industry collapsed, but a few properties such as the Groverake and Frazer's Hush were still being operated at a reduced level as late as 1999. Environmental restrictions on the use of chlorinated fluorocarbons, coupled with competition from subsidized fluorite production in China, ultimately brought an end to fluorite mining in England, despite the fact that significant reserves surely remain in many of the mines.

For further information on the history of mining in the Weardale district see Fisher (2004), Fairburn (1996), Hunt (1970), Raistrick and Roberts (1984) and Dunham (1990).

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MINES

Blackdene Mine

The Blackdene mine began operating in 1401, and during the mid to late 20th century it became one of the most productive fiuorite mines in the district. Originally mined for lead in the late 1800s by the Beaumont Company, it followed the Blackdene vein northeastward from the Wear River, producing over 14,000 tons of lead between 1818 and 1861. It was shut down in the 1870s or 1880s, but reopened in 1908 as a fluorite mine under a succession of owners who worked both the Blackdene vein and the Slitt vein. In 1973 a new incline driven to access unmined portions of the Slitt vein encountered many open crystal-lined vugs, and produced many of the finest specimens preserved in collections today. The mine finally closed in 1987.

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Fluorite from the Blackdene mine most commonly occurs as cubic crystals in medium to dark shades of purple, but pale green and yellow crystals have also been found, typically in attractive association with dolomite, calcite, quartz or lustrous galena of complex habit. Bright microcrystals of pyrite and chalcopyrite are commonly found scattered over some surfaces of the fluorite crystals. Gemmy fluorite crystals from Blackdene reach 5 cm on edge, and opaque crystals to 20 cm on edge are known; Lindsay Green bank long kept a decorative piece in his home which features an astonishing 35-cm single crystal (shown on page 74, top).

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Specimen supplies have always been spotty and, in the absence of documentation, the collecting date of specimens has typically been difficult or impossible to determine; it was always more common to see individual pieces, very likely from recycled, older collections, than to see lots of freshly collected specimens. In the late 1970s, Black dene mine specimens with beautiful purple and dark green fluorite crystals to 15 cm associated with brilliant galena crystals appeared on the market, probably from the Slitt vein. In early 1986, just before the mine closed, a large pocket was discovered in a new drift, and about 40 good specimens were marketed soon afterwards; these measure from 2 to 10 cm.

Blue Circle Cement Quarry

The Blue Circle Cement quarry, where the Portland cement process was developed, lies very near the classic Heights mine and Cambokeels mine fluorite localities. Begun in the 1960s, the quarry closed in 2003, having sporadically yielded fine green fluorite specimens for almost 50 years. The fluorite crystals are simple cubes in classic penetration twins; they are a typical "English" sea-green, and transparent, but many have purple zones near their centers. They are generally a paler green than the crystals from the Rogerley mine and the Heights quarry. In the mid-2000s (after the quarry closed), a few Blue Circle specimens were recovered showing purple color or a deep golden yellow color resembling that of fluorite from the Hilton mine; commonly these have a thin zone of purple color just below the surface.

Blue Circle quarry fluorites are easy to confuse with fluorite specimens from other places in northern England, and probably are quite rare on the market, at least in the United States; a small lot was offered in California in the early 1990s. As of 2002, the quarry was closed, its plant and landmark chimney had been demolished, and the site was undergoing reclamation.

Boltsburn Mine

The Boltsburn mine workings, opened as a lead mine in the early 1800s, follow the northeast-trending Boltsburn vein. It was originally worked by the Beaumont Company, and was rich in fluorite but carried only modest levels of galena. Beaumont gave up its leases in the 1880s, after the crash in lead prices, and the mine was taken over by the Weardale Lead Company. In 1892 miners following galena stringers away from the vein encountered extremely rich, highly mineralized replacement bodies about 6 meters from the vein. Mining proceeded to gradually greater depths until 1932, when the mine was closed because of labor and transportation problems. Exploratory drilling in the 1970s revealed that much ore still remains in the unmined portion of the replacement body, but it would probably be too expensive to mine.

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Mineralization was developed along three horizons (the High Flats, Middle Flats and Low Flats) which merge with each other; individual flats were up to 25 feet thick and extended up to 200 feet from the vein. Crystal-lined cavities several feet in height and up to 50 feet long were encountered. These cavities contained large amounts of crystallized galena and well-developed, highly transparent fluorite crystals to more than 20 cm. Watson (1904) described entering such a cavity, walking over 6-inch cubes of translucent, bluish violet fluorite, some of them studded with sparkling crystals of calcite or quartz, finding a perfect 12-inch cubic crystal of fluorite, and marveling at the solid coating of galena crystals across the roof of the pocket.

The Boltsburn mine is famous for particularly large and transparent crystals of lavender to purple, yellow and pale olive-green fluorite, lustrous cuboctahedral crystals of galena, and "nail-head" calcite, sometimes in association with siderite, drusy quartz, sphalerite, pyrite and rare chalcopyrite.

Cambokeels Mine

The Cambokeels mine, which exploited a section of the Slitt vein extending from the nearby Blackdene mine, was worked for lead by the Beaumont Company from 1868 to 1871; the relatively wide vein was nevertheless poor in lead values, and the mine was soon abandoned. It was reopened for fluorite in 1905 and was worked intermittently thereafter, closing in 1989. From the early 1970s until 1989 it was among the most prolific producers of fluorite in the Weardale district. Operators put in a new incline below the old Horse level, discovering high-grade fluorite below the 40-meter level; working levels were established at 200, 240, 280, 320 and 340 meters, making it the deepest mine in the district.

Hundreds of cavities lined by crystals of quartz, calcite, pyrite and fluorite (surprisingly, there were very few sphalerite crystals, even though the ore ran to as much as 20% ZnS) were encountered on the 320 level during the 1980s. Most of the cubic fluorite crystals are purple or colorless, but green to ice-blue crystals up to 5 cm on edge were found in the Zinc Flats on the 320 level; the crystals are lustrous, transparent and beautiful, occurring in large clusters dusted with microcrystals of pyrite. A single cavity opened in 1989 on the 340 level yielded fine specimens showing twinned, gemmy lavender to lilac-pink fluorite crystals on white quartz matrix. The miners were adamant that this fluorite had a deep red color underground, but changed color when brought to the surface. Pyrite crystals in quartz were found above the 320 level.

Notable specimens that have been found include superb purple, green, pale pink and blue fluorite. And Britain's best pyrrhotite specimens were collected from a few pockets found in the lower workings just before the mine closed in 1989. The lustrous crystals, most of them loose individuals, are bronze-colored, sharp, and characteristically slightly curved and etched; they reach 10 cm across. Initially the miners discarded many specimens, taking them simply for an odd kind of pyrite.

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Milky white calcite crystals were found in the Cambokeels workings in a wide variety of habits, including paper-thin hexagonal plates, hexagonal tablets, simple rhombobedrons, and pseudocubic and "nailhead" forms. Some of the analcime crystals found on the dump by government geologist Brian Young were acquired by Lindsay Greenbank.

Frazer's Hush Mine

The Frazer's Hush mine exploited the Greencleugh vein, a western extension of the Red vein near the Groverake mine. The underground mine workings date from the 1970s, but the mine is named for a nearby site that had been worked by "hushing" (hydraulic overburden removal) in medieval times. Although the mine was in decline commercially by the late 1980s, it still managed to produce many fine fluorite specimens from a series of cavities encountered between 1988 and 1999 when the mine closed. Patricia Greenbank made many collecting trips to the mines during those years, and acquired what is probably the finest large Frazer's Hush specimen from that era (LG-471).

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Typical Frazer's Hush specimens display extremely glassy, transparent, twinned fluorite crystals showing purple to dark sea-green or indigo-blue color, some reaching 5 cm on edge. They are highly fluorescent, even in sunlight. Fluorite may be associated with galena, marcasite, sphalerite, calcite, siderite and ankerite; and fluorite crystal groups totally coated with glittering crusts of galena microcrystals have also been found.

In the late 1980s the mine yielded large specimens with transparent, gray-violet to purple cubic crystals, commonly penetration-twinned and displaying tetrahexahedron faces; in 1990 a cavity on the 340 level gave up abundant specimens showing purple cubic crystals on matrix, some with good galena crystals. In the mid-1990s, a number of substantial pockets produced lustrous, purple, twinned fluorite crystals to 3 cm which rest on cavity-lining layers of smaller fluorite crystals (e.g. the one shown above). In 1998, on the 360 level, matrix plates as large as 10 X 20 cm were dug, these with transparent purple fluorite cubes to 1 cm on edge grown thickly over massive green, vein-lining fluorite, with 1-cm cuboctahedrons of galena. Cubic fluorite crystals to 30 cm on edge were found during the late 1980s in the Great Limestone workings, but these very large crystals are of poor quality. The Frazer's Hush mine finally closed in 1999, by which time its underground workings had been connected with those of the Groverake mine.

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Greenlaws Mine

The Greenlaws mine, originally operated during medieval times, exploited two parallel veins. It was worked for lead by the Beaumont Company from 1850 to 1884, after which the lease was picked up by the Weardale Lead Company until 1897. The mine was reopened briefly in the 1940s but has been idle since then, except for the activities of collectors. The mine was worked for specimens in the late 1990s, producing amber-yellow to dark purple cubic fluorite crystals to 10 cm on edge. The crystals, however, are not as lustrous or transparent as the best from other, better known Weardale localities.

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Groverake Mine

The Groverake mine is located at the confluence of the Groverake vein, the Greencleugh vein and Red vein. Mining probably began there in the 1600s, but major mining by the Beaumont Company began in the late 18th century, initially for lead. The veins proved to be rich in fluorite but rather poor in lead, and yielded only about 6,500 tons of lead concentrate between 1818 and 1883 when the market price for lead crashed. During World War II, under the British Steel Company; the mine became one of the leading producers of fluorite in the district. Weardale Minerals and Mining came in when the steel industry was privatized, but went bankrupt in 1991, at which time the mine was acquired by Sherburn Minerals and worked until closing in the summer of 1999. It was the last commercially active fluorite mine in the North Pennines.

Fluorite specimens from the Groverake mine are rare, and not especially good by the region's general standards. They consist of groups of simple cubic crystals of a pastel green color unlike that of fluorite from any other Weardale mine. The mine apparently worked entirely within veins and did not encounter any major replacement bodies that would have included large cavities--a fact which probably accounts for the scarcity of specimens found there.

Heights Mine

The underground Heights mine, opened in 1847, operated on three different veins: the roughly parallel Heights North (a likely continuation of the Greenlaws West vein) and Heights South veins and the intersecting West Cross vein. The Heights mine was worked briefly for lead in the 1860s by the Beaumont Company, but was operated principally for limonite by the Weardale Iron Company between 1850 and 1868. The replacement bodies proved to be very vuggy, yielding superb specimens of transparent, colorless to pale purple and deep green, penetration-twinned fluorite crystals to 10 cm. Many Heights mine fluorite crystals are dotted with tiny colorless calcite crystals.

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Commercial activity finally ceased in the early 20th century, but the mine was popular with field collectors for many years. A major collecting effort at the Heights mine was undertaken in 1976 and 1977 by a party headed by Peter Briscoe, who, on one of these dangerous trips underground in the old workings, opened a 3 X 5-foot pocket (called "the Green Hole") which yielded about 35 superb fluorite specimens with lustrous green, transparent, penetration-twinned cubic fluorite crystals to 3 cm on edge. Access to the underground workings was still possible (with difficulty) in 1979, when Peter Bancroft accompanied Lester Jackson on a visit and found pale green penetration-twinned cubic crystals to 2 cm on edge, but a few weeks later the old tunnels were blasted shut.

In the early 1990s, after a change of management, the old South vein and the West Cross vein, once worked underground, were worked again in the Heights quarry, just to the east of the old mine, and collectors once again had access to this famous fluorite locality. Opaque, deep green cubic fluorite crystals to 12 cm were collected from mud-filled cavities on the West Cross vein, and more fine specimens were dug near the South vein: good milky purple to gray, blue-green and "classic" bottle-green fluorite crystals emerged and were marketed during the 1990s. However, as of the mid-2000s, illicit collecting has led to a ban on digging in the quarry.

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Middlehope Shield Mine

The Middlehope Shield mine in Middlehope Burn north of West-gate, accessed by an adit called White's level, is the earliest of the Weardale mines known to produce collector-quality specimens of emerald-green, penetration-twinned fluorite (Fisher, 2006). Records indicate that the mine was active some time before (1809, and mineralogist Edward Daniel Clarke (1819) made special note of a large find of good specimens there. White's level penetrated several major ore-bearing veins (including what may be a continuation of the Heights West Cross vein) in the Quarry Hazle sandstone unit just below the Great Limestone formation, and consequently the fluorite specimens are distinctive for having a sandstone matrix. The mine was in operation at least through 1864.

Unlike some of the more famous Weardale mines, White's level was never reopened in the 20th century, and was never described in the mineralogical literature, so it has remained relatively unknown. The workings have since collapsed and the area is now a protected archeological site where collecting is forbidden.

Redburn Mine

The Redburn mine is a modern operation begun in 1964 by the Weardale Lead Company and soon taken over by Swiss Aluminium UK. A well-mineralized portion of the vein was worked for a distance of over 300 meters, and a second section discovered 1,200 meters away was worked for another 610 meters. The mine closed in 1981 when the economic reserves were exhausted.

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Though not a major source of collector-quality fluorite specimens, the Redburn mine did produce some attractive specimens of a pale green to medium-green to purple color, showing both twinned and untwinned crystals associated with quartz, calcite and sulfides. Specimens of jackstraw cerussite were also recovered, unusual for this district and for the British Isles. The Greenbanks kept for their collection one of the largest specimens recovered (shown here, page 93) and one of the most aesthetic small cabinet pieces, as well.

Rogerley Mine

The Rogerley mine, driven into the side of an abandoned limestone quarry of the same name, has produced some of the very best of the variously styled fluorite specimens from the Weardale region. And, unlike most of the other famous Weardale localities, it has done so liberally in very recent times. The Rogerley limestone quarry began working in the mid-1800s; specimen-quality fluorite was first noticed and saved (as far as is known) by collector Raymond Blackburn in the early 1970s.

From 1972, Lindsay Greenbank and Mick Sutcliffe ran a specimen-mining operation here, producing gorgeous deep green (and highly fluorescent purple), transparent cubic fluorite crystals, as individuals and penetration-twins to 2 cm covering matrix. These specimens from the "Sutcliffe vein" trickled out sparsely onto the general market, sometimes misattributed to the Eastgate mine. Rarely, purest blackberry-purple crystals were also found in the same vein (an early piece is shown here, from the Michael Sutcliffe collection). Lindsay suffered an overwhelming illness in 1996, after which mining here was stopped and the rights sold to two of his friends in the United States, Jesse Fisher and Cal Graeber.

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Beginning in 1999, the American consortium called UK Mining Ventures, led by Cal Graeber and Jesse Fisher, leased the mine and began rehabilitating the workings, also seeking specimens. The walls of a 35-meter adit driven into the wall of the old quarry were sprayed with pressurized water, and the UK Mining Ventures group almost at once found an interconnected series of pockets which began yielding great numbers of wonderful fluorite specimens. The crystals are penetration-twinned, and reach 3.5 cm; they are uniformly dark green, though some have purple zones in their cores or around their outsides. Their fluorescence is so intense that they glow blue or purple in ordinary sunlight. Associated species include drusy milky quartz and corroded, octahedral galena crystals.

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In the summer of 1999, about 1,800 specimens came out, ranging from loose 3-cm twins to great matrix plates 60 cm across, in addition to profligate swarms of thumbnails, and this was the start of the near-flooding of the general market with beautiful Rogerley fluorite. In the summers of 2001 and 2003, gorgeously colored fluorite crystal groups were mined from the West Cross Cut in the Rogerley mine; superb specimens to 3 X 5 cm appeared at the Ste.-Marie-aux-Mines show of that year. The summer of 2007 was also a very good collecting season, with clusters of gorgeous crystals to 4 cm individually, and crystal-blanketed matrix plates to 20 cm across, emerging from pockets the collectors named the "Jewel Box" and the "Rat Hole"; many of these specimens were marketed in Denver in the same year. For a thorough account of specimen-recovery work at the Rogerley mine during the early 2000's, see Fisher and Greenbank (2003).

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The 2009 collecting season at the Rogerley mine was only modestly successful. Many fine specimens were recovered in June, but then the zone they had worked so successfully for the past couple years finally petered out. July and much of August were spent driving a new exploratory tunnel, during which a few smaller pockets were encountered. UK Mining Ventures is currently the only large operation devoted entirely to specimen recovery in the British Isles.

West Pastures Mine

The West Pastures mine operated on the West Pastures vein, near the Stanhopeburn mine, but its early history is unknown. Simple cubic crystals of pale apple-green fluorite to several centimeters on edge were collected at the West Pastures mine during the 1970s when it reopened briefly for the mining of large decorative pieces; unfortunately the color of fluorite from this mine is light-sensitive, and most specimens have by now faded from an attractive apple-green to a dull yellowish brown. The Greenbank collection retains one large specimen, kept in a drawer to avoid fading. Later collecting in the mine produced specimens showing yellow and dark purple fluorite crystals, as well as more of the apple-green crystals.

Whiteheaps Mine

The Whiteheaps mine operated on a series of interconnected veins (mainly the White, Ramshaw and Jefferson veins). The earliest workings for argentiferous galena probably date to the early 1700s, but after the mid-1880s, mining concentrated primarily on fluorite. Blanchard Fluor Mines, Ltd. took over the mining leases in 1940, but the mine was nationalized in 1967 and passed to the British Steel Company; in 1982 it was taken over by Weardale Mining and Processing, but mining ceased in 1987.

Whiteheaps mine fluorite is typically purple to lavender and occurs in crystals to several centimeters that are commonly found coated by small, blocky quartz crystals. Other minerals found there include galena, pyrite, sphalerite, marcasite and pyrrhotite.

St. Peter's Mine

The St. Peter's mine vein near Spartylea in East Allendale was discovered accidentally in 1902 in the course of finishing the Blackett Level. The St. Peter's vein consisted primarily of galena in a fluorite gangue. Lead values decreased with depth, eventually becoming subordinate to zinc (sphalerite). The vein was thought at the time to be the continuation of Swinhope vein. The St. Peter's mine closed in 1946 when the Great Limestone formation carrying the ore-bearing veins and flats was found to be truncated on the west by glacial sediments filling the East Allen Valley. All that remains aboveground today are some old concrete foundations of mine buildings.

Some of the finest apple-green fluorite specimens ever found in Britain came from the St. Peter's mine in the 1930s, collected by Sir Arthur Russell, who later donated them to the British Museum. Attractive (though lesser) clusters of lustrous, untwinned purplish gray and amber-colored fluorite with siderite overgrowths were found in the mine and marketed in the U.K. in the mid-1990s, but Russell's original location for the legendary green fluorite has never been rediscovered. Groups reach large-cabinet size. Ankerite, calcite and quartz have also been reported. The St. Peter's mine has recently been worked for specimens by Dave Hacker and Northern Minerals.

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Author:Wilson, Wendell E.; Moore, Thomas P.
Publication:The Mineralogical Record
Geographic Code:4EUUK
Date:Jan 1, 2010
Words:4158
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