GUIDE i" nil-; mim;i;.\i.ih;i, COLLECTIONS 49 



SEMIMETALS 



Arsenic. Arsenic is usually found in massive forms, the 

 structure being reniform, and is composed of concentric layers 

 which can frequently be separated with ease. Crystals are 

 quite rare. The color is tin-white, tarnishing to black, and the 

 luster is nearly metallic. It occurs in veins in crystalline rocks 

 and in the older schists. 



Antimony. Usually found in massive forms, lamellar or radi- 

 ated, of a tin-white color and metallic luster. Rhombohedral 

 crystals are of rare occurrence. 



Bismuth. Bismuth is found in brittle, silver-white, arbores- 

 cent forms which, on a fracture of the ground mass, resemble 

 Hebrew characters; also foliated and granular. The luster is 

 highly metallic and the color white, sometimes taking a reddish 

 tinge. It is rarely found in distinct hexagonal crystals. 



METALS 

 Gold An 



Gold is usually found alloyed with small amounts of silver 

 and sometimes copper and rare metals. Distinct isometric 

 crystals are rare though skeleton crystals and distorted octa- 

 hedrons in wirelike, arborescent and reticulated shapes are 

 quite common. Nuggets, grains and scales are also charac- 

 teristic, usually disseminated through the gold-bearing rock in 

 such small quantities as to be perceptible only by assay methods. 

 It is of a fine yellow color, has a metallic luster and is extremely 

 malleable and ductile. 



Gold occurs in veins, usually in quartz rock, where it is asso- 

 ciated with sulfids, specially pyrite. It is largely mined from 

 superficial deposits of sand, gravel and boulders formed in the 

 valleys and river bottoms from the erosion of higher rocks con- 

 taining gold veins. These beds of gold-bearing material are 

 .called placers. 



Gold is used chiefly for coinage, jewelry ami gilding. 



