Unlike gold, silver freely enters into compounds with the non-metals, which is the reason that it is not found primarily in its native state, but usually as a sulphide. Its ultimate source is in the igneous rocks, few granites or lavas, on analysis, failing to show at least traces of silver. Before it is available as an ore, or mineral, it has been dissolved from the original magma, and segregated in fissures or veins, along with such minerals, as quartz, fluorite, calcite, etc. This seems to have taken place while the igneous rocks were still hot, and by the agency of vapors and liquids which were also hot. The presence of silver in sedimentary and metamorphic rocks, or even in sea water, is secondary. The primary deposition of silver is usually in the form of sulphides, the commoner of which are, argentite or silver sulphide, pyrargyrite or silver and antimony sulphide, and prousite, or silver and arsenic sulphide. Its occurrence as native silver, or the chloride, cerargyrite, is secondary and due to the reactions which have taken place when sulphide deposits have been subjected to weathering agents. The United States produces about 25% of the world’s supply, Mexico some 35%. It is especially found along the Cordilleran ranges of both North and South America. Silver Ag Pl. 6 Usually non-crystalline, but occasionally showing cube or octahedron faces of the isometric system; hardness 2.5; specific gravity 10.5; color silvery white; luster metallic; opaque. When found in its native state silver is usually in wirey, flakey, or mossy masses; but sometimes masses of considerable size occur, the most famous being an 800 pound nugget found in Peru, and another of 500 pounds weight found at Konsberg, Norway, and now preserved in Copenhagen. When exposed to the air the surface soon tarnishes and takes on a black color which must be scraped off to see the real color. Like gold, silver is usually found associated with other metals, like iron, copper, lead and zinc; and much of the silver recovered is obtained in connection with the mining, especially of copper and lead. Some lead ores have so much silver in them that they are better worth mining for the silver; galena, for instance, under such circumstances being termed argentiferous galena. Native silver is a secondary mineral, having been formed by the reduction of some one of its sulphides by water, carrying various elements which had a greater affinity for the sulphur. Silver is found along with copper in the Lake Superior region, and in Idaho, Nevada, and California. Argentite AgS Pl. 6 _silver glance_ Usually in irregular masses, but sometimes in cubes; hardness 2.5; specific gravity 7.3; color and streak lead gray; luster metallic; opaque on thin edges.