Value.—An ore of zinc.
Localities.—Found in limestone with Garnet and Zincite.
31.—Galena.
Occurs
in crystals and masses; brilliant lustre; brittle; easily broken;
powder, when finely rubbed is black; can be cut with a knife; heated it
gives off sulphur and melts ; dissolves in nitric acid leaving a white
powder at the bottom; gravity 7-5—or a little heavier than cast-iron.
Value.—The
main source of lead (yielding eighty per cent), and »lso smelted for
the silver it contains. Used also in glazing stone-ware.
Localities—Generally found in limestone with Iron Pyrites, zinc-ore, etc. That found in slate is richest in silver.
32.—Garnet.
Occurs
in crystals with four-sided faces; often nearly round; deep-red, which
grows darker by heat; rarely yellow ; also in brown masses ; melts at a
high heat; brittle; not scratched by a knife; glassy lustre; gravity 4.
Value.—The clear deep-red and yellow varieties are used for jewelry; the massive brown is ground for "emery."
Localities.—Found in slate and granite rocks.
33.—Gold.
Occurs
in scales, grains and nuggets, or disseminated through cellular quartz;
metallic lustre; without tarnish ; can be cut and hammered into thin
plates; not dissolved by nitric acid; gravity 19, when pure and of a
rich gold yellow color. The pale or brass yellow specimens are much
lighter, the gravity being as low as 13. A grayish yellow gold,
occurring in small, flat grains has a gravity of about 16.
Localities.— Found
in veins of quartz running through greenish or grayish slates, the
quartz at the surface being generally full of cavities and rusted, and
the slates below the surface often containing little cubic crystals of Iron Pyrites: also in the valleys traversed by mountain-streams and in the river sands and gravel below. Iron and Copper Pyrites, Galena and Blende frequently
contain gold. Masses of quartz and pyrites from the gold-regions, which
make no show of gold, sometimes pay well; the value of such specimens
can be determined only by an assayer.
34.—Graphite.
Occurs
in foliated, scaly and granular masses; can be cut into thin slices
which are flexible, but not elastic ; impressible by the nail; feels
greasy; leaves a shining trace on paper; metallic lustre; not altered
by heat or acids • gravity 2.
Value.—Used for pencils, polishing, glazing, for making steel, crucibles, overcoming friction, etc.
Localities.—Found in granite, slate and limestone rocks.
35.—Gray Copper Ore.
Occurs
in crystallized or granular masses; metallic lustre; color between
steel-gray and iron-black ; brittle; the powder dissolved in nitric
acid makes a brownish green solution; melts at a red heat; gravity 5.
Value.—An ore of copper (containing thirty-three per cent.) and silver, of which Nevada specimens have sixteen per cent.
Localities.—Found with gold, silver and lead.
36.—Gypsum.
Occurs
in plates, fibres coarse and fine, and massive; pearly or glistening,
powder white, which if heated and mixed with water, turns hard; does
not dissolve in sulphuric acid; may be scratched by the nail; gravity
2*3.
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