The Mineral realgar

Realgar is an historically important mineral, with a striking ruby-red color that stands out in the mineral kingdom. The rare transparent lustrous forms are truly masterpieces in mineral aesthetics.

Realgar is a photosensitive mineral and will alter to Pararealgar upon prolonged exposure to light. Pararealgar is unstable and will eventually crumble into a yellow powder if left in the light. The alteration mineral that Realgar transformed into was generally assumed to be Orpiment, but recent scientific analysis has in fact determined the orange alteration product as Pararealgar. Due to the instability of Realgar, specimens should be stored enclosed and covered to prevent their exposure to light. Occasional exposure to look at a specimen will not cause damage; only prolonged or repeated exposure will cause alteration. Several important museums have had Realgar on display consistently exposed to light, and these specimens can be seen altered and crumbled.

Realgar contains a significant amount of poisonous arsenic, and is itself somewhat toxic. Washing hands is recommended after handling Realgar specimens, especially if they are powdery.

Chemical Formula

AsS

Color

Bright red

Crystal System

Monoclinic

Properties

Streak Orange to reddish-orange

Hardness 1.5 - 2

Transparency Transparent to translucent

Specific Gravity 3.5 - 3.6

Luster Adamantine, resinous, dull

Cleavage 2,1

Fracture Conchoidal

Tenacity Slightly sectile

Other ID Marks Transforms into yellow Pararealgar upon prolonged exposure to light.

Crystal Habits

Crystals are prismatic and stubby, and may be in irregular groups. Crystals are usually heavily striated lengthwise, and may be well-terminated or rectangular in shape. Also drusy, encrusting, botryoidal, grainy, massive, and in earthy masses.

3D Crystal Atlas

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Additional Information

Composition Arsenic sulfide

In Group Sulfides; Simple Sulfides

Striking Features Striking color and low hardness

Environment In low-temperature hydrothermal veins, volcanic hot springs, arid borate deposits, and occasionally in metamorphic marble pockets.

Rock Type Igneous, Sedimentary, Metamorphic

Other Names

Ruby Sulfur

Uses

Realgar is an important ore of arsenic. It is used in the manufacturing of fireworks, and was historically used as a red pigment. Realgar is also an important collectors mineral, and the transparent gemmy forms are especially desired.

Noteworthy Localities

Some of the best Realgar crystals come from the Rumanian Transylvania at Baia Sprie (Felsöbánya), as well as Cavnic (Kapnik), both in Maramures Co. Outstanding transparent gemmy crystals are well known from the Jiepaiyu (Shimen) Mine, Hunan Province, China. Bright red though small Realgar crystals in contrasting white marble came from the Lengenbach Quarry, Wallis, Switzerland. Realgar occurs with Colmanite in the borate deposit of Bigadiç, Marmara Region, Turkey; and it occurs in dark red crystals in the Palomo Mine, Huancavelica, Peru.

In the U.S., the most outstanding occurrences are the Getchell Mine (and nearby Turquoise Ridge Mine), Humboldt Co., Nevada; and the Royal Reward Mine (and Cardinal Reward Mine), in the Green River Gorge, King Co., Washington. Both these localities have produced exceptional crystals of sharp color and relatively large sizes. Other U.S. occurrences are Manhattan, Nye Co., Nevada; Boron, Kern Co., California; and Mercur, Tooele Co, Utah.

Common Mineral Associations

Orpiment, Pararealgar, Calcite, Quartz, Barite, Cinnabar, Stibnite, Ulexite, Colemanite

Distingushing Similar Minerals

Cinnabar and Crocoite - Greater hardness and specific gravity.

realgar Photos

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