Jiepaiyu Mine, Shimen, Hunan Province, China

Realgar: Jiepaiyu Mine, Shimen, Hunan Province, China

Robert B. Cook

There has been a dramatic increase recently in the awareness of the environmental impact of minor amounts of arsenic, including that from natural sources. Consequently, arsenic minerals that have been of interest to exploration and economic geologists for many decades are only now coming into their own in the geologic and environmental community as a whole. Although the list of arsenic-rich minerals is not particularly long, their individual geochemistries and geologic occurrences are quite varied. Orpiment ([As.sub.2][S.sub.3]) has already been covered in this column (Cook 2000), and it is now appropriate to discuss its sister species, realgar, one of the most intensely red of all minerals and one currently available from several unusual sources.

When occurring in good specimens, realgar is relatively easy to recognize because of its bright red to orange-yellow color coupled with a resinous to greasy luster. It is soft with a hardness of 1.5-2, is sectile to brittle, has a specific gravity of about 3.6, and has good cleavage on {010} and less well-developed cleavage on {101}, {100}, {120}, and {110}.

Realgar is monoclinic (2/m) and occurs in variably striated prismatic crystals that are reported to reach lengths of 12 cm. It forms contact twins on {100}. It is commonly seen in massive or fine granular forms or as incrustations and inclusions in other minerals.

Realgar is simple arsenic sulfide (ASS). Published chemical analyses typically show no other constituents are so close to the ideal composition. The mineral is dimorphous with pararealgar, which is also thought to be monoclinic. On long exposure to light it disintegrates to a yellow powder composed of pararealgar (a polymorph of realgar) commonly together with another poorly described arsenic sulfide. Yet another red polymorph known as beta-AsS is believed to be represented by “realgar” from Pampa Larga, Chile; it does not decompose.

Realgar is most frequently encountered in epithermal (near-surface, low-temperature) hydrothermal settings such as shallow veins, hot springs, and fumaroles. It is an uncommon accessory mineral in certain sedimentary carbonate and clay-rich rocks and has been identified as a product of coal-mine fires. Commonly associated minerals include orpiment, stibnite, a variety of sulfides and sulfosalts, calcite, and barite.

Realgar rarely occurs in the eastern United States. It has been reported from two pegmatite localities: the Ryerson Hill mines at Paris, Oxford County, Maine, and the Palermo No. 1 mine, Groton County, New Hampshire. It occurred with jordanite in zinc ores mined at Balmat, Edwards County, New York (Jensen 1978). It was a rare mineral in zinc ores at Sterling Hill, Sussex County (Palache 1941) and was an unusual mineral occurring in calcite at the Lower New Street trap-rock quarry at Paterson, Passaic County, New Jersey. It is a very rare accessory mineral in the Winnfield salt dome, Winn Parish, Louisiana.

Realgar is well known from certain occurrences in the western United States, particularly gold deposits of the general Carlin type in Nevada (Castor and Ferdock 2004). Perhaps best known to collectors are the attractive groups of crystals from the Getchell mine, Humboldt County, where individual crystals to 12 cm have been found associated with orpiment, fluorite, calcite, galkhaite, laffittite, cinnabar, stibnite, and getchellite (Stolburg and Dunning 1985). Exceptional specimens have also been recovered from the White Caps mine at Manhattan, Nye County. Here, realgar occurs in crystals to 3 cm associated with calcite, orpiment, wakabayashilite, and stibnite (Gibbs 1985). Other geologically similar occurrences include the Gold Bar mine, Antelope district; several locations in the Cortez district; the famous Carlin mine and, with fluorite, calcite, and orpiment, at the nearby Gold Strike mine, Eureka County; mines in the vicinity of Jerrett Canyon, Elko County; the Lone Tree, Ogee, and Pinson mines, and prospects in the National district, Humboldt County; the Battle Mountain district, Lander County; the Manhattan Consolidated, Paradise Peak, and Round Mountain mines, Nye County; and prospects on Alligator Ridge, White Pine County. It occurs on hot-spring sinter at Steamboat Springs, Washoe County.

Exceptionally fine realgar specimens have been recovered from white to buff-colored calcite veins cutting sandstone and shale at the Royal Reward and Cardinal Reward mercury mines and nearby Okay coal mine in the Green River Gorge northeast of Franklin, King County, Washington (Dillhoff and Dillhoff 1991). Here, well-developed transparent to translucent crystals to 5 cm across occur with cinnabar, stibnite, and quartz scattered over the surface of specimens that reach 23 cm across. Other interesting Washington realgar localities include the Alverson mine at LaConner, Skagit County, where the mineral is found with celestine and strontianite; the American arsenic mine at Reiter, the Bonanza Queen mine at Silverton, and the Foggy, Mystery, O and B, Pride, and Justice mines at Monte Cristo, Snohomish County; mines on Storm King Mountain in the Republic district, Ferry County; and the Mineral Creek mine at Anderson Lake, Lewis County (Cannon 1975).

Realgar occurs in scattered Utah localities. These include the Brickyard, Golden Gate, Mercur, and Sacramento mines in the Mercur district, Tooele County; the Vipont mine in the Ashbrook district, Box Elder County; the Fumerol No. 2 mine in the San Rafael district, Emery County; the Hampton mine in the Coyote Creek district, Garfield County; the Manning mine, Utah County; and the Bingham district, Salt Lake County (Bullock 1967).


A number of relatively minor yet interesting California realgar localities are given by Murdoch and Webb (1966). These include apparent evaporitic occurrences in the Kramer area of Kern County; Tick Canyon, Los Angeles County; and with pirssonite, hanksite, and halite in salt beds at Searles Lake, San Bernardino County. Realgar also occurs as small prismatic crystals in cracks in sandstone at Skaggs Springs, Sonoma County; from near Deadwood, Trinity County; with sulfur and claudetite at a sulfur prospect near the 4S Ranch, Imperial County; the famous Commercial quarry at Crestmore, Riverside County; and the Morning Star and Monitor mines, Alpine County.

Other reported realgar occurrences in the western United States include small crystals apparently formed as an alteration product of tennantite in the Greenhorn prospect, La Plata district, La Plata County, Colorado; unspecified locations near Castle Springs in the Bradshaw Mountains, Yavapai County, and near the junction of the Gila River and Hackberry Wash, Pinal County, Arizona; the Valentine mine, Black Pine district, Cassia County, Idaho; the Carbonate Creek mine, Kingston district, Sierra County, New Mexico; prospects in the Horse Heaven district, Jefferson County, Oregon; and the Rambler mine in the Encampment district, Carbon County, the Norris Geyser Basin in Yellowstone National Park, and the Goodhope mine in the Atlantic City district, Fremont County, Wyoming.

Several interesting Canadian realgar occurrences are listed by Traill (1983). The mineral occurs with native arsenic and calcite near Wolf Lake and along Watson Bar Creek, and it is one of the main ore minerals in the quartz vein exploited in the Mount Washington copper deposit near Courtenay, Vancouver Island, British Columbia, where it occurs with orpiment, duransite, and pararealgar. It is found with scorodite in vuggy calcite in the Stewart mine, Little Harbour, Newfoundland, and is a minor mineral in ores of the Keeley mine, South Lorrain Township, the David Bell mine at Hemlo, and the Madsen mine at Red Lake, Ontario. It occurs with orpiment, arsenopyrite, and quartz in the Daulton and Venus mines at Windy Arm, Tagish Lake, Yukon. Other reported occurrences include mines at Port Radium on the shores of Great Bear Lake, Northwest Territories, and the Grey Rock mine on Truax Creek, Lillooet mining division, British Columbia.

Realgar is relatively uncommon in Mexican ore deposits (Panczner 1987). It is reported from both the San Antonio and E1 Potosi mines in Aquiles Serdan (Santa Eulalia), Chihuahua, where it occurs in crystals to about 5 mm with quartz, calcite, galena, and iron sulfides. It is apparently of limited distribution in the Velardena mine at Cuencame and the Ojuela mine, Mapimi, Durango. Other Mexican localities include the Noche Buena mine, Zacatecas; the San Juan Nepomucno mine, Queretaro, where it occurs sparingly with orpiment; and the Encino Largo, Jacala, and the Lomo del Toro mine, Zimapan, Hidalgo.

Realgar is reported from a variety of scattered South American localities. From Bolivia, Rivas and Ahlfeld (1998) report acicular realgar crystals occurring in cavities in sphalerite found in the San Juan mine in the Buena Vista district; small acicular crystals of both reaglar and orpiment on arsenopyrite collected at Llallagua, Potosi; an unusual occurrence of realgar and ferberite in the Magarinos mine at Ancoraimes; an occurrence at Buena Vista (Lipez) with orpiment, stibnite, and jalpaite; and several fumarolic and hot-spring occurrences where crystals to about 1 cm have been found. It is reported from several occurrences in and around the Atacama Desert of Chile, including Pampa Larga at Tierra Amarilla. It has been found in the Loma Blanca borate deposit at Coranzuli, Jujuy, and at the famous rhodochrosite occurrence in the Capillitas mine, Catamarca, Argentina. Relatively minor realgar occurs with other sufide minerals in the Sacramento mine, Julcani district; unspecified mines of the Castrovirreyna district; the Casapalca district; the Atacocha district with exceptional orpiment; the famous rhodochrosite and silver occurrences at Uchucchacua; and sparingly with orpiment at Quiruvilca, Peru (Crowley, Currier, and Szenics 1997).


Small amounts of realgar have been reported from a large number of European occurrences, generally related to relatively recent volcanism, limestone or dolomite quarries, or base- and precious-metal deposits. It is particularly well known as crystals to 7 cm occurring with a suite of complex and extremely rare sulfosalts at the Lengenbach quarry, Binntal, Valais, Switzerland. It occurs as minute crystals and coatings in Vesuvian lavas, La Solfatara at Pozzouli, on Mount Etna, Sicily, and elsewhere in Italy and is a minor though interesting trace mineral in marbles quarried at Carrara and Seravezza in the Apuan Alps. Other Italian occurrences include the Morone and Niccioleta mines, Grosseto Province, and the Cetine mine, Siena Province, Tuscany; and the Molinello mine, Genova Province, Liguria. It is well known from the Adamio No. 2, Plaka mine No. 80, and elsewhere in the Lavrion district, Greece. It is reported from Mareshnitsa, Haskovo Oblast and Dobroseletz, Yambol Oblast, Bulgaria, and is well known from Jachymov, Czech Republic. French localities include the Gabe Gottes mine, Alsace, the Matra mine, Corsica, and an unusual occurrence in the Decazeville Coal Basin. Almost twenty Austrian realgar occurrences are reported in the literature and include several lignite mines in the Lavant and Lower Drau valleys; marble quarries at Stelzing and Trixen in the Saualpe Mountains, Carinthia; the Schwarzleo district, Salzburg; and the Brixlegg-Schwaz district, Tyrol.

German realgar occurrences are widespread and include mines in the Schauinsland lead-zinc district; the Saint Josefi and Michael mines, Reichenbach; and mines at Burgfelsen, Bockelsbach Valley, and Heubach Valley, Wittichen, Baden-Wurttemberg. It is a well-known mineral in ores recovered in the Annaberg-Buchholz, Freiberg, and Schneeberg districts, Saxony, and at Wolfsberg, in the Harz Mountains. It is also an interesting though rare mineral in marbles quarried at Nieder-Beerbach and Bensheim, Odenwald, and is an accessory mineral in the uranium occurrence at Ronneburg, Gera district, Thuringia. At one time specimens with realgar crystals to 2 cm were found in the Rollenberg railway tunnel near Bruchsal.

Realgar, locally in fine specimens, has been recovered from a significant number of occurrences located in the Carpathian Mountain region of eastern Europe (Udubasa et al. 2002). It occurs in prismatic crystals to 2 cm long associated with quartz, orpiment, galena, and sphalerite in sedimentary units near Baligrod, Poland. At least ten occurrences are known in Romania, including Moldova Noua where prismatic crystals to 3 cm long have been collected; 4-cm crystals associated with arsenic, stibnite, barite, and sphalerite in the famous mines at Baia Sprie; crystals to 5 cm with quartz, barite, and ankerite at Sacaramb; the mines at Cavnic; with intergrowths of stibnite near Baia Mare; and in marls and sedimentary breccias with sulfur, orpiment, and aragonite at Covasna. Prismatic realgar crystals to 5 cm associated with orpiment occur in limestone near Kraliky, Tajov, and Sumiac, Slovakia. Realgar crystals to 3 cm occur in the Vyshkove district, Ukraine.

The finest and certainly largest realgar crystals currently available originate in the Jiepaiyu realgar mine at Shimen, Changde district, Shimen County, northwestern Hunan Province, China. Here, realgar is found in sharply developed, nearly transparent crystals to 12 cm long associated with orpiment, calcite, and picropharmacolite. Attractive groups to 40 cm across have been recovered.

Realgar apparently occurs only rarely in Australia. It was, however, an interesting component of ores in the Great Boulder Proprietary and the Golden Horseshoe mines at Kalgoorlie, Western Australia, where it had an unusual vertical range, occurring from the surface down to 750 meters (Simpson 1952).

Other interesting realgar occurrences include the Crven Dol mine at Allchar, Macedonia, where it is found as crystals to 1.5 cm; the Gomi As-Sb-Hg deposit, Georgia; the Busange gold property, Kalimantan, Borneo, Indonesia; the Zarshuran mine, Takab, Iran; the Nishinomaki and Nishizawa mines, Kanto district, and the Nyu mine, Kinki district, Honshu Island, the Monji me in Miyagi Prefecture, the Teine mine in Hokkaido, and the Nifu mine in Mei Prefecture, Japan; the Bota-Burum uranium deposit at Alakol Lake, Kazakhstan; the Chauvai and nearby Sb-Hg deposits in the Osh district, Kyrgyzstan; gold occurrences on Lihir Island, Papua New Guinea; the Gal-Khaya As-Hg-Sb and similar deposits, Eastern Siberian region, and the Lenskoye Mo-U deposit, Far Eastern region, Russia; the Chiufen mine, Jui-Fang, Taiwan; the Emet borate deposit, Turkey; the Ustarasai bismuth deposit, Tashkent district, Uzbekistan; and even the great Tsumeb deposit of Namibia.



The manuscript was improved materially by the helpful reviews of John S. White of Kustos, Stewartstown, Pennsylvania, and Bob Ramik of the Royal Ontario Museum, Toronto, Canada.


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Robert B. Cook

Department of Geology and Geology

Auburn University

Auburn, Alabama 36849-5305


Robert B. Cook, an executive editor of Rocks & Minerals, is a professor of geology and head of the Department of Geology and Geography at Auburn University, Auburn, Alabama. He welcomes suggestions for this column and can be contacted at the addresses above.

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