SMITHSONITE
	This mineral, named after James Smithson, who founded the Smith­sonian Institution in Washington, is a carbonate of zinc used chiefly as an ore of that metal. It is usually of a dull, earthy character and poorly fitted for ornamental purposes. In some occurrences, however, it exhibits pleasing colors and a translucency reminding one of onyx. When so occurring it may be cut into ring stones, or even vases and other dishes of considerable size and beauty. The smithsonite from Laurium, Greece, is that perhaps most extensively used in this way, its color usually being some shade of blue. From Siberia a beautiful bright green smithsonite is obtained, the green color being due probably to a little admixed copper, and from the zinc mines of Arkansas and Missouri a bright yellow form is derived, known locally as "turkey fat ore." The yellow color here is due to a little cadmium. All of these forms of smithsonite exhibit when polished a rich luster and subtransparency which are pleasing. The hardness of the mineral is somewhat deficient for enduring wear, this being but 5. It is rather heavy, its specific gravity being 4.3 to 4.4. It is infusible, but soluble in hydrochloric acid with effervescence. When heated before the blowpipe a coating is formed, which is yellow when hot and white on cooling. These tests serve to distinguish the mineral from any others with which it might be confounded. 203