Realgar is an arsenic sulfide mineral. It was originally called “ruby sulfur” in early times because of its rich red to orange-red color and noxious components. This is why Realgar really is a sexy red mineral. Realgar has a long history of use as a poison (“bull’s blood”) in ancient Greece as well as a medicine in traditional Chinese and Indian Ayurvedic practices. From ancient times, cultures from the Mediterranean region to China used Realgar to produce red pigment until the 18th century. Other traditional uses included manufacturing lead shots, printing, and dyeing calico cloth. Tanners used it as a hair remover. Today, Realgar shows up in the manufacturing of fireworks.
Realgar is very soft. Hardness is only 1.5 – 2 on the Moh’s scale. Realgar is rarely found as a faceted gemstone for several reasons. In addition to being very soft, it is sectile and has good cleavage which presents challenges to faceting. Also, stones are rarely transparent. Furthermore, Realgar decomposes slowly in light and turns into yellow, even softer, Pararealgar. Finally, Realgar also contains arsenic and sulfur and should not be worn as jewelry.
That being said, Realgar has brilliant red crystals and is highly valued by mineral specimen collectors. Enclose and cover specimens for prevention of exposure to light. Occasional exposure to look at a specimen will not cause damage; only prolonged or repeated exposure will cause alteration. Wash hands after handling Realgar as a mineral specimen.
Realgar is a polymorph with Pararealgar, meaning that they share a common chemical formula As4S4 but belong to different crystal systems. This mineral belongs to the Monoclinic Crystal System, prismatic Crystal Class. Realgar crystals are prismatic and stubby and maybe in irregular groups. Crystals display usually heavily striated lengthwise and maybe well-terminated or rectangular in shape. Other Realgar habits are drusy, encrusting, botryoidal, grainy, massive, and earthy masses. Realgar occurs in low-temperature hydrothermal veins (especially with ores of lead and silver), volcanic hot springs, arid borate deposits, and occasionally in metamorphic marble pockets.
Noteworthy localities: Some of the best Realgar crystals come from Baia Sprie, as well as Cavnic, both in Maramures County, Romania. Outstanding transparent gemmy crystals are well known from the Jiepaiyu Mine, Hunan Province, China. Bright red though small Realgar crystals in contrasting white marble came from the Lengenbach Quarry, Wallis, Switzerland. Realgar occurs with Colemanite in the borate deposit of Bigadiç, Marmara Region, Turkey. It occurs as dark red crystals in the Palomo Mine, Huancavelica, Peru.
Moreover, In the United States, the most outstanding occurrences are the Getchell Mine (and nearby Turquoise Ridge Mine), Humboldt County, Nevada; and the Royal Reward Mine (and Cardinal Reward Mine), in the Green River Gorge, King County, Washington. Both of these localities have produced exceptional crystals of sharp color and relatively large sizes. Other U.S. occurrences are Manhattan, Nye County, Nevada; Boron, Kern County, California; and Mercur, Tooele County, Utah; and in the geyser deposits of Yellowstone National Park.
Article by Bill Jones of Sidewinder Minerals.