PYRITE (Lat. pyrites, from Gk. repirr, flint. millstone, relating to fire, from rilp, pyr, fire). An iron disulphide that crystallizes in the isometric system, has a metallic lustre, and is of a brass-yellow color. It is widely dissemi nated, occurring in rocks of all kinds and of all ages, sometimes in the form of grains disseminat ed throughout the mass of a rock or along the line of contact between basic eruptives and sedi mentaries ; as irregular and sporadic and con cretionary masses in sedimentary rocks and modern sands and gravels; in the form of true fissure veins; and as interbedded, often lenticu lar masses, sometimes of immense size. lying conformably with the stratification of the in closed rock. The origin of the mineral in the older crystalline rocks is frequently somewhat obscure, but in sedimentary rocks it is regarded as due to the precipitation of the included fer ruginous matter by sulphureted and deoxidizing solutions produced by decomposing animal and vegetable matter. When found on the surface the mineral is often considerably altered by oxidation and hydration, forming limonite. Py rite is found in many localities, including Frei berg, Saxony; Pribram, Bohemia; Schemnitz, Hungary; Langban, Sweden; Kongsberg, Nor way; Cornwall and Derbyshire, England; and Peru. In the United States numerous localities
where large crystals occur are known in Maim, New Hampshire, Vermont, Connecticut, New York, Pennsylvania, Virginia, North Carolina, Colorado, and California. The amount produced in the United States in 1901 was 234, S25 long tons, valued at $1,024,449. The mineral finds its principal use in the manufacture of sul phuric acid and ferrous sulphate (green vitriol). Small quantities are used in the manufacture of vermilion paints, and some varieties are cut into squares, ovals, and other shapes for use as set tings for rings, scarf pins, trinkets, etc. Owing to its yellow color, pyrite has been frequently called fool's gold, and many stories are told of the disappointment of miners, who, thinking they had found a fortune, were nndeceived only when the mineral was submitted to experts.
The name pyrites is applied by Dana to a group of isometric sulphides and arsenides, in cluding, besides that of iron. those of manganese, cobalt, nickel, etc.