THE NONMETALLIC MINERALS. 183 



II. SULPHIDES AND ARSENIDES. 

 1. REALGAR. 



This is a monosulphide of arsenic, AsS, = sulphur 29.9 per cent; 

 arsenic, 70.1 per cent; hardness, 1.5 to 2; specific gravity, 3.55; color, 

 aurora red or orange yellow, streak the same. 



2. ORPIMENT; AURIPIGMENT. 



A trisulphide of arsenic, of the formula As 2 S 3 , = sulphur 39 per cent, 

 arsenic, 61; hardness, 1.5; specific gravity, 3.4 to 3.5. Color, lemon 

 yellow. This mineral occurs usually associated with realgar at the 

 localities mentioned below. 



Occurrences. Realgar and orpiment are very beautiful, though not 

 abundant minerals which occur associated with ores of silver and lead 

 in various European mining regions and also those of Japan (Specimen 

 No. 11864, U.S.N.M.), Hungary (Specimen No. 66813, U.S.X.M.), 

 Bohemia, Transylvania, and Saxony. They have been reported in 

 the United States in beds of sandy clay beneath lava in Iron County, 

 Utah, and form the so-called "Arsenical gold ore" of the Golden Gate 

 Mine, Mercur, Tooele County, this same State (Specimen Xo. 53363, 

 U.S.N.M.); also in San Bernardino County, California; Douglas 

 County, Oregon (Specimen No. 62101, U.S.N.M.), and in minute 

 quantities in the geyser waters of the Yellowstone National Park. 



The realgar and orpiment of the Coyote mining district. Iron County, 

 Utah, occur in a compact, sandy clay, occupying a horizontal seam or 

 layer about 2 inches thick, not distinctly separated from the clay, 

 but lying in its midst in lenticular and nodular masses. The bulk of 

 the layer consists of realgar in divergent, bladed crystals, closely and 

 confusedly aggregated, sometimes forming groups of brilliant crystal- 

 line facets in small cavities toward the center of the mass. The orpi- 

 ment is closely associated with the realgar in the form of small and 

 delicately fibrous crystalline rosettes, and small spherical aggregations 

 made up of fine radial crystals, and also in bright yellow, amorphous 

 crusts in and around the mass of the realgar. Fine parallel seams of 

 gypsum occur both above and below the layer, and the strata of arena- 

 ceous clays above for 30 feet or more are charged with soluble salts 

 which exude and effloresce upon the surface of the bank, forming hard 

 crusts. The whole appearance and association of the minerals indi- 

 cates that they have been formed by aqueous infiltration since the 

 deposition of the beds. 1 



Orpiment is said 2 to occur at Tajowa, near Xeusohl, Hungary, as 

 nodular masses and isolated crystals in clay or calcareous marl. 



1 W. P. Blake, American Journal of Science, XXI, 1881, p. 219. 

 2 H. A. Miers, Mineralogical Magazine, July, 1892, p. 24. 



