COPPER, a dyad metallic element; symbol, Cu.; at. wt. 63.6; sp. gr., 8.95; melting point, 1,091° C. Copper is a red malleable, ductile metal, occurring in a native state on the S. shore of Lake Superior. It also occurs to a greater ex tent as copper pyrites of a brass yellow color as peacock ore, characterized by its iridescent colors, in the Butte mines, Montana; as gray copper ore, a sulphide, in Cornwall and Freiberg; as indigo copper, so called from its color, in Chile; as malachite, or green carbonate, in Si beria and Australia; and as azurite or blue carbonate in Burra Burra, Aus tralia.
Copper forms several alloys. Brass is an alloy of two-thirds copper and one third zinc; bronze, gun-metal, and bell metal are alloys of copper with tin. Cop per forms two series of compounds, the cuprous and cupric salts. Copper ar senite, or Scheele's green, is used as a pigment for wall papers; it is very poi sonous. Copper salts are detected by giving in an acid solution a black pre cipitate with H,S. All salts of copper are poisonous. Verdigris is an acetate of copper, often formed by cooking food in copper vessels.
Production.—Since the census year 1880 the United States has risen to the rank of the largest copper producer in the world, outstripping by far any other country. The production of copper in the United States in 1919 was 1,310, 541,529 pounds. The production in 1918 was 1,908,533,595 pounds. The largest
production was from Arizona, which con tributed 536,513,368 pounds. Michigan was second with 201,716,335 pounds, and Montana third with 176,189,873 pounds. The production of Utah was 148,057,450 pounds. Other States producing over 50,000,000 pounds were New Mexico and Nevada. Alaska produced 50,534,992 pounds. The total value of the produc tion in 1919 was $243,761,000, compared with a value in 1918 of $471,408,000. The imports of copper ore in 1919 amounted to 49,716,511 pounds. There were imported 263,220,449 pounds of un refined black copper, and copper in bars, pigs, or other forms. The exports of copper in 1919 amounted to 516,627,776 pounds.
Historp.—Copper has been known since prehistoric times. There may have been a copper age before that of bronze. The latter compound metal, an alloy of cop per and tin, was known long before brass had been made. The word copper occurs once in the Old Testament (Ezra viii : 27), but what is in many places called brass should have been rendered copper. Cop per was in use in ancient Assyria. The classical nations were familiar with it. The Gree.ks brought it from Cyprus, the mines being at Tamassus, near Fama gosta. Copper mines were first opened in England A. D. 1189, but not very suc cessfully till A. D. 1689.