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Chinese fluorite.

Of all the minerals which have come from China in fine specimens since about 1990, fluorite has thus far been the most abundant and most varied in habit, color and associations. Many specimens are oiled or otherwise objectionably enhanced by Chinese middlemen, but the fact remains that some Chinese fluorite localities are of world-class importance, and more discoveries may be expected.

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INTRODUCTION

When the first new mineral specimens from China began appearing on the mineral Western market in the late 1980's and early 1990's, enormous stibnite crystals, fine cinnabar crystals and fascinating specimens of realgar and orpiment were among the highlights which provided a new impulse to collecting activities. Offerings of Chinese minerals grew considerably over the next few years, generally without full and precise locality information in most cases. Such information has since appeared in only a few publications, e.g. Bancroft (1997), Liu (1995), Behling et al. (2002), Hawthorne (2002) and Ottens (2003). The present article is intended to fill the informational gap regarding Chinese fluorite, now commonly offered on the market.

THE MARKET FOR CHINESE FLUORITE

When minerals appeared for sale in the Western world after the opening of China, fluorite specimens from Hunan were quickly numbered among the most interesting items. Aesthetically attractive clusters of pale blue Shangbao fluorite crystals, many of them transparent, were highly coveted. In 1995, abundant beautiful specimens of green fluorite were produced from the Xianghualing mining district. The Chinese dealers, having learned quickly that fluorite is quite easy to sell, then developed more localities as supply sources. Especially notable among these is the Yaogangxian mine, with sharp blue cubic crystals. Most recently, violet and green crystals of various forms embedded in white quartz matrix have come from mines in Jiangxi and Guangdong provinces. The selection of Chinese fluorite specimens available has turned out to be extraordinarily varied with respect to forms, colors, associations and localities. It is heartening that the miners have learned so quickly to collect specimens with the utmost care, so that undamaged specimens may be offered in quantity. Unfortunately, however, the well-motivated dealers have learned how a dull luster, or damage to crystals, may be concealed. Consequently, fluorite specimens in China are commonly stored in water, or are "improved" with all sorts of oils, or with hairspray or silicone. It is regrettable that at mineral shows, fluorite specimens are oiled right under the eyes of customers--and not only by Chinese dealers--and nevertheless are sold.

It should be noted that most of the fluorite offered in the form of collector specimens is found as a gangue mineral in ore veins, in deposits mined for other minerals. But, interestingly, at about 4 million tonnes per year (Zho Xun et al., 2002), China leads the world in fluorite production, and provides more than half the world's total. Fluorite is mined in almost every province, from nearly 900 deposits.

The most important deposits for industrial purposes are in the provinces of Zhejiang, Fujian, Hunan and Guizhou. No collector-quality fluorite has been reported from most of these occurrences, although a few deposits do produce beautifully color-banded massive material from which artistic objects such as sculptures, bowls and figurines have been fashioned. Especially attractive are the very thin bowls made of violet and green-banded fluorite with natural pyrite coatings around their rims. An astonishing crafts-manship and feeling for form shows forth in these beautiful and fragile objects.

China inherits an ancient tradition of working jade into fine artistic creations, and by "jade" one certainly does not just mean jadeite or nephrite; many other minerals, and not least fluorite, are used in the decorative arts as jade substitutes. Whereas in earlier centuries the majority of the people could not afford to acquire "jade" sculptures, they can be acquired much more cheaply today thanks to the use of more common materials and to mass production techniques. The wide spectrum of offerings now includes not only sculptures made from pale greenish fluorite but also animal figures, pyramids, obelisks, etc., made from interestingly color-banded material. Also, the people who attribute special esoteric powers to earth materials are fond of tumbled stones and other artifacts made from Chinese fluorite.

To date, fluorite is certainly the Chinese mineral of greatest abundance on the Western market. Some of the more important occurrences are examined more closely below.

MAJOR FLUORITE SPECIMEN OCCURRENCES

Hunan Province

Of particular significance is Hunan Province, where 37 fluorite-bearing deposits and 43 other occurrences of fluorite have been investigated. Of the deposits, seven produce fluorite as an industrial byproduct. One example is the Taolin lead/zinc deposit, which, besides being a source of interesting mineral specimens, has a remaining reserve of 60 million tonnes of fluorite. The world-famous polymetallic deposit of Shizhuyuan, in the southern part of the province, has a proven reserve of 45 million tonnes of fluorite; up to now, only a few collector pieces from Shizhuyuan have come on to the market, despite intensive mining. One of the reasons why so much collector-quality fluorite has been found in Hunan Province particularly may be that a great many of the ore deposits there were formed by the intrusion of granitic magmas into older sedimentary rocks, and cracks and fissures in the latter make ideal environments for the formation of fluorite crystals.

One of the deposits classified as belonging to the "polymetallic sulfide" type, and greatly enriched in tin, is Xianghualing, in the Nanling Mountains, about 80 km southwest of Chenzhou in Linwu County--a region rich in ore deposits. Discoveries of ancient copper-smelting ovens and mine workings have dated the earliest mining activities here to 907-960 A.D. During the Ming Dynasty (1573-1620 A.D.), in addition to earlier tin and arsenic mines, lead/zinc mines were worked at Taipingli, Caiyuanzi, and other sites in the Xianghualing area. The Xianghualing orebody, extending over an area of 36 square km, is emplaced in Devonian sedimentary rocks with intrusions of Mesozoic-age granites. With regard to mineralization and the relationship between ore and country rock, the deposit can be assigned to different genetic types: a granitic tantalum/silver deposit, a hydrothermal tin/beryllium and tin/lead/zinc deposit, and a tin-bearing occurrence in sandstone. The formation and distribution of the fluorite bodies is a result of hydrothermal activity and intermittent tectonic events.

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In the Xianghualing district, ore is taken from several large mines and from numerous small, unconnected workings. These workings are visible from a distance on the steep slopes of the mountain. The district includes mines directly adjacent to the village of Xianghualing, and mines at Xianghuapu and Dongshan. Presently the ore reserves are nearing exhaustion, but new, interesting occurrences in the region certainly await discovery. As soon as sufficient capital and foreign investment become available, new mines will be opened in the vicinity of Xianghualing. Uranium minerals are of special significance with a view to energy supplies.

At an elevation of about 1,594 meters on Mount Xianghualing there is a cassiterite mine; however, it produces no collector-quality specimens of cassiterite, as it is a greisen deposit, with the ore finely divided in country rock. The significance of this deposit for collectors is that between 1996 and 1998, large quantities of deep green fluorite in cubic crystals to more than 10 cm were found there. Specimens with deep green and totally transparent cubic crystals are highly coveted; green octahedral crystals with matte luster are rarer. Also, fluorite specimens showing crystals of a later generation and different habit overgrown on earlier crystals are characteristic of Xianghualing (Rustemeyer, 2002). In the most commonly observed specimens of this type, cubic crystals rest on octahedral ones; in a few discoveries, the first generation of octahedral crystals is overgrown by a thin quartz crust, upon which rest cubic crystals of the second fluorite generation. Faden crystals of fluorite are another specialty of Xianghualing.

Calcite occurs commonly, in some cases as flattened, very thin crystals, in others as rhombohedral crystals to 10 cm. In long-wave ultraviolet light, some of the fluorite fluoresces blue, and some of the calcite fluoresces bright orange. Rarely, scheelite is found as white crystals to 1 cm. Some of the fluorite discoveries at Xianghualing have attracted special attention, and commanded very high prices, because of the great size, intense color, and clarity of the crystals. Unfortunately, this popularity has led to the use of irradiation to "improve" the green color of what were originally unremarkable specimens. This artificially induced color is not stable, however; after several months, or a year, the crystals revert to a pale hue. Any calcite present in the irradiated specimens changes in color also--from white to brownish gray.

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A great rarity from the deposit--until recently known only from Xianghualing, its type locality--is hsianghualite, a lithium and beryllium-bearing zeolite which belongs to the isometric system and forms face-rich, almost spherical white crystals to 3 mm in diameter.

The mine at Xianghuapu, lying halfway between Linwu and Xianghualing, is also of great interest for collectors. This polymetallic occurrence chiefly produces tungsten and tin. The fluorite which occurs there is commonly green with brownish interior color zones, but large, sharp, colorless and bright blue, cubic fluorite crystals have also been found there recently. At the end of 2003, some pockets in fissures yielded bright green, exceptionally transparent fluorite crystals showing cubic and rhombic-dodecahedral forms, overgrown by pink calcite. To date, the Xianghuapu mine has produced no specimens in which fluorite is associated with crystallized quartz.

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Work has already ceased in the region of the former scheelite mine at Dongshan, which lies only 6 km north of the town of Linwu, the county seat. Only a few of the workings in the old district are still being mined on a private basis. The scheelite ore is extensively overgrown by fluorite, and rare specimens exhibit scheelite crystals to 5 cm protruding from massive yellow-brown scheelite. Fluorite from Dongshan is attractive chiefly for its total transparency and high luster. Its colors vary from almost colorless through bright blue and bright green, and crystals reach 10 cm. Until a short time ago, unfortunately, no special care was taken to collect specimens without damage; therefore, the very best specimens date only to very recent times. One of the specialties of the Dongshan skarn deposit is pale green fluorite with blue-colored zones at the corners. Typical associated species include pink dolomite and white quartz in short-prismatic crystals. Massive galena and sphalerite are found at the deposit's contact with granite.

Not far from Chenzhou lie three important mines: Huangshaping (lead/zinc), Shizhuyuan (a polymetallic deposit, with tungsten and bismuth), and Yaogangxian (tungsten). Up to now, Huangshaping and Shizhuyuan have produced only a few interesting specimens for collectors. Shizhuyuan has mainly given up very good manganocalcite, and occasionally galena and sphalerite; however, early in 2003 the Chinese dealers began offering specimens from a new discovery of bright green fluorite from Shizhuyuan. The transparent crystals reach 3 cm, and in contrast to their contemporaries from Xianghualing they display a combination of the hexahedron {100} and the rhombic dodecahedron {110}. They are remarkably well formed. These specimens come from a mine called Dongpo, Shizhuyuan district, about 25 km southeast of Chenzhou. The green fluorite crystals are characteristically overgrown in part--on three faces at most--by small, white, flattened rhombohedral crystals of calcite.

In the Nanling Mountains in the southern part of the province of Hunan, not far from the border with Guangdong, lies the huge Yaogangxian tungsten mine--about 50 km southeast of the prefectural capital of Chenzhou, in Yizhang County. Mining here began around 1914. At times employing more than 5,000 people, the Yaogangxian is one of the most important mines in Hunan, producing more than 1500 tonnes of wolframite and other ores (including scheelite and cassiterite) per year. Presently, though, the future of the established mines is uncertain, as the State wants to close or sell off several mines which are no longer economically viable, and the Yaogangxian, with its complex geology and its consistently expensive mining technology, seems imperiled.

The geological situation at Yaogangxian is complex (Li Yiqun and Yan Xiaozhong, 1991; Song Shuhe et al., 1992). The orebody penetrates a granite and overlying sandstone of Cambrian age, as well as a Devonian shale and overlying limestone. The surrounding skarn and the gangue contents of the ore veins are most important for collector-quality minerals. More than 200 ore veins up to 1000 meters long and 1300 meters deep are known; the veins can be more than 2 meters thick. Some of the minerals, including ferberite, arsenopyrite, stannite and fluorite, are found in quartz veins, while others, including scheelite, chalcopyrite and bismuthinite, are found in the skarn. Tungsten ores also occur as finely divided particles in a greisen-type stockwork.

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Fluorite occurs most commonly in cubic crystals only a few millimeters on edge; rare examples in which the crystals reach 4 cm or so are highly coveted. The color ranges from pale to medium blue and is uniformly distributed; color-zoned crystals with dark blue cores are found only rarely. Octahedral fluorite crystals, both blue and deep green, are also among the rarities of Yaogangxian. Some unusual finds have been described in which a first generation of octahedral crystals is overgrown by a second generation of cubic crystals. A particular fascination of specimens from Yaogangxian lies in the association of fluorite with quartz, ferberite, arsenopyrite and other species, creating highly aesthetic effects. Some fluorite crystals appear blue-green and have a matte luster; a close inspection of these reveals inclusions of countless hairlike crystals of jamesonite. Once in a while, irradiated specimens of Yaogangxian fluorite are offered. If the crystals rest on quartz or are associated with calcite, these species will show a blackish or brownish discoloration if they have been irradiated.

The pyrite mine formerly worked at Shangbao is, without a doubt, among the most important fluorite localities in Hunan Province, but this locality will be described in a separate article in a forthcoming issue.

The Taolin lead/zinc deposit, 37.8 square km in extent, lies about 170 km north of Changsha, 20 km east of Yueyang (the administrative seat of Yueyang Prefecture) and 15 km south of Linxiang. The deposit lies between granite (Song Shuhe et al., 1992), a slightly metamorphosed Precambrian sandstone, and a red Tertiary conglomerate. The emplacement of the orebody was influenced by faulting. This lead/zinc/fluorite body counts as one of the largest high-temperature hydrothermal vein occurrences in China. Galena and sphalerite are the chief ores mined; they are only occasionally found as good specimens, sphalerite in particular being noted as honey-brown crystals to 10 cm. Most galena crystals found show combinations of cubic and octahedral faces, and have a matte luster. Fluorite is very common, and has been recovered in very large groups of green, translucent to transparent crystals. There is no dominant form, but essentially the crystals are octahedral, and there is a later generation of cubic crystals. White, tabular barite crystals are associated with fluorite on some specimens, for a beautiful color-contrast.

Jiangxi Province

The province of Jiangxi is blessed with numerous very important deposits and mining areas--among them the tungsten occurrence in the Dayu Mountains, the rare earth-element mines in the Nanling Mountains, and the copper mines at Jiujiang and Dexing. For several years, however, no fluorite specimens were known from these mining regions. Chinese dealers first offered specimens of white quartz matrix with violet fluorite crystals at the Tucson and Ste.-Marie-aux-Mines shows of 2002. The face-rich, commonly quite transparent crystals have been partially freed from the enclosing quartz by hydrofluoric acid treatment, and as a rule they have (when not oiled) a matte luster. Single crystals to 4 cm in diameter are especially attractive. Most of these crystals display combinations of cubic and rhombo-dodecahedral faces, and appear almost spherical. Originally their locality was given as Yiwu, in Zheijiang Province, but eventually it became known that the true locality was the De'an fluorite workings at Wushan, near De'an, in the county of the same name, in Jiangxi Province. In the open-pit workings at Wushan, fluorite is found in limestone, the fluorite being overgrown by a quartz layer between 5 mm and 5 cm thick, with the terminal faces of quartz crystals sometimes well developed. The largest fluorite crystal ever found in the mine, 160 cm in diameter, is displayed in the courtyard of an administrative building in Wushan.

Preparation of specimens by etching quartz away from the fluorite is done, not in De'an, but in a headquarters for such work in Chenzhou, in southern Hunan Province. From this place, at the end of 2003, green-blue octahedral fluorite crystals also emerged onto the mineral market. In order to keep the real locality secret, a great number of specimens were falsely labeled, unfortunately, as having come from De'an. According to a communication from a reliable source, the true locality is in the Ganzhou area, about 500 km south of De'an but also in Jiangxi Province. The region is easy to reach from Chenzhou, about 200 km west of it. For now "Ganzhou" must suffice as a locality designation.

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Regrettably it is customary in China to keep secret for a long time the real names of deposits which offer interesting collector-quality minerals. Although prices asked in China for large plates of etched quartz with fluorite crystals can far exceed $1,000, the dealers who offer the material in Chenzhou are not ready to provide precise locality information. Many such dealers who buy the specimens and bring them to Changsha (the Chinese headquarters of mineral dealing) or to Europe do not know the real locality, and may themselves believe the false attribution.

Mineral dealers in Chenzhou have specialized in etching fluorite out of quartz. In order not to use too much hydrofluoric acid (which is dangerous to handle) and to reduce costs, the blocks of quartz with embedded green fluorite are cut into flat slabs, so that the quartz can be partly or wholly dissolved away with relatively little use of acid. The fluorite etched out in this way consists of octahedrons to 5 cm, commonly as thin plates of mutually attached crystals. The predominant color is green, but with zones of blue. The luster is uniformly frosty, so that specimens either show an attractive play of colors when backlit or, if oiled, display a bright luster. Because they have been exposed by etching, most of the crystals are undamaged. Plates more than a meter long and 60 cm wide have been prepared.

Zhejiang Province

It should be mentioned at this point that besides the market for collector pieces of interest to Westerners, a demand has developed in China, during the last ten years, for large "decorative" specimens. At no time in the history of China has collecting minerals been as important as it has long been in Europe. Minerals have, however, been sought and valued as materials used for pharmaceutical purposes. Further, naturally formed stones on which weathering has bestowed unusual shapes or interesting structures appeal strongly to the aesthetic sense of the Chinese and also have been closely related to the teachings of Taoism. Large mineral specimens which would not be salable at all, or only with great difficulty, in the west are easily sold in China, even if they show obvious damage. This is as true for fluorite specimens as for calcite, quartz, pyrite, or stalactites. Thick plates with green fluorite from Yiwu, Zhejiang Province are particularly well suited for such "decorative" purposes. From a layer of fluorite about 10 cm thick protude crystal formations from 5 to 10 cm across, showing no particular habit.

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Guangdong Province

From the province of Guangdong, which borders Hunan on the south, deep green octahedral fluorite was offered first in 2002. These crystals come from Ruyuan, Lechang County, and, like the crystals from De'an, are exposed by dissolving away a white quartz matrix.

Guizhou Province

Among the more unusual fluorite occurrences is the Dushan mine near Mawi, Guizhou Province, where violet fluorite crystals, only a few mm on edge, form overgrowths on stibnite.

Fujian Province

From Fujian Province, specimens with spessartine, smoky quartz and cream-colored feldspar crystals are aesthetically impressive, and therefore highly valued, and such specimens are still more desirable when fluorite crystals also appear on them. The spessartine collecting sites lie in the mountains of the southeastern coast, one near the village of Tongbei, Yunxiao County, the other, 30 km distant, at Yunling, Zhangpu County. Reportedly, fluorite crystals appear only on specimens from Yunling. The minerals are dug, exclusively for collectors' purposes, from steep, unvegetated mountain slopes. Fluorite occurs predominantly as blue octahedral crystals; however, quite recently bright green crystals and crystals of cubic habit have been observed. As a rule the fluorite crystals from this locality measure around 2 cm, the largest so far seen measuring 15 cm.

Sichuan Province

Rare "association" pieces for fluorite collectors come from the region of Xuebaoding, Pingwu County, Sichuan Province. Mines between Pingwu and Songpan on Xuebaoding Mountain, in the Minshan Mountains, produce fluorite with scheelite, cassiterite and beryl. The cubic crystals are colorless, bluish or greenish; most display a frosty luster, and few are larger than 2 cm, although one notable discovery produced crystals to more than 15 cm on edge. The most highly coveted specimens are those which display the associated species characteristic of this locality, namely orange scheelite, colorless to pale blue beryl, cassiterite and quartz.

Xinjiang Province

There is considerable potential for fluorite specimens in the Altai Mountains of Inner Mongolia and in Xinjiang Province. In the years between 2000 and 2003, a great number of specimens with dark violet, face-rich crystals came onto the market from this region. Since nearly all of the crystals have been etched out with acid, the faces are frosty. To date, the Artaishan mine at Nanjiang has been given as the locality, but this must be regarded as doubtful. So far the locality has not been verified by serious Chinese dealers or by western visitors, and locality data in such cases must always be regarded as provisional.

Other Regions

Not all Chinese fluorite specimens which have appeared so far have been attributed to definite localities. Such is the case, for example, for the blue cubic crystals resting on faces of smoky quartz crystals, and for the very beautiful bright blue cubes on dolomite allegedly from somewhere in Guangdong.

In the coming years, a series of new discoveries of the much-cherished mineral fluorite may be expected from a multitude of ore deposits and richly mineralized regions in China.

BIBLIOGRAPHY

BEHLING, S. C., LIU, G., and WILSON, W. E. (2002) Stibnite from the Wuling antimony mine, Jiangxi Province, China. Mineralogical Record, 33, 139-147.

LIU, G. (1995) Zinnober und Antimonit: Ausgezeichnete Kristalle und ihre Fundstellen in China. Lapis, 20 (10), 33-43.

LI YIQUN and YAN XIAOZHONG (1991) Mineralogy of Tungsten Deposits in Nanling and Neighboring Areas, China. Wuhan: University of China Geoscience Press.

OTTENS, B. (2003) Minerals of China. Presented at the 30th Mineralogical Symposium, Rochester, N.Y., April 3-6, 2003.

OTTENS, B. (2003) Der Wolframbergbau Yaogangxian in China. Lapis, 28 (11), 13-23.

OTTENS, B. (2004) Fluorit aus China. ExtraLapis, 26/27 44-55.

RUSTEMEYER, P. (2002) Verruckte Fluorite. Lapis, 27 (9), 13-28.

SONG SHUHE et al., Eds. (1992) Mineral Deposits of China, Vol. 2. Beijing: Geological Publishing House. 355 pages.

ZHO XUN et al., Eds. (2002) Mineral Facts of China. Beijing: Science Press. 776 pages.

Berthold Ottens

Klingenbrunn Bahnhof 24

D-94518 Spiegelau

Germany
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Title Annotation:mining industry
Author:Ottens, Berthold
Publication:The Mineralogical Record
Geographic Code:9CHIN
Date:Jan 1, 2005
Words:3946
Previous Article:Xuebaoding: Pingwu County, Sichuan Province, China.
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