242
GOLD AND GEMS.
Value.—A gem; clear specimens weighing over four carats, are valued at half the price of the diamond.
Localities.—Found in granular limestone and clay, 69.—Steatite.
Occurs
in masses, consisting of minute pearly scales or grains; can be marked
by the nail; hardens by heat; soapy feel; gravity 2-5.
Value.—Used for fire-stones, tubes, in manufacture of porcelain, etc.
Localities.—Found in beds with limestone, serpentine and slate. 70.—Strontianite.
Occurs in crystals and in fibrous or granular masses • glassy lustre ; brittle ; thin pieces melt before a blow-pipe tinging the flame red; effervesces with acids ; gravity 3-6.
Value.—A source of nitrate of strontia used in fire-works.
Localities.—Found in limestone.
71.—Sulphur. Occurs
in crystals, masses and crusts; brittle; can be easily cut; burns with
a blue flame and sulphur odor; gravity 2.
LOCALITIES.—Found in limestone and gypsum, and around geysers and sulphur springs.
72.—Tin Ore.
Occurs
in crystals, grains and masses; high lustre; powder gray or brownish;
brittle; will strike fire with steel; unaltered by heat or acids;
gravity 7,—being nearly as heavy as lead-ore.
Value.—The only ore of tin, containing seventy-nine per cent. No gold-mine ever paid such profits as the tin mines of Cornwall.
73.—Topaz.
Occurs in crystals; glassy lustre; brittle; scratches rod-crystal; not acted upon by ordinary heat or acids; gravity 3.5.
Value.—A gem; the most esteemed are the rose-red and white. Localities.—Found in granite.
74.—Tourmaline.
Occurs
in crystals, usually in long, slender three-sided prisms which break
easily, glassy lustre ; brittle; becomes milk-white by [heat; scratches
rock-crystal and garnet; gravity 3.
Valuk.—Used for jewelry.
Localities. -Found in granite rocks.
75.—Variegated Copper Ore.
Occurs
in crystals and masses'; metallic lustre ; quickly tarnishes ; color
between copper-red and-light-brown ; powder pale grayish-black;
dissolves in nitric acid; at a high heat melts to a copper globule;
heated on charcoal gives off fumes of sulphur; gravity 5.
Value.—An important ore of copper yielding sixty per cent.
Localities.—Found in granite, free-stone, etc., with other ores.
76.—Wad.
Occurs
in masses; earthy and loose; can be broken by the fingers, and soils;
no lustre; melted with borax makes a violet glass; feels very light.
Value.—Used in bleaching and for making smalt.
Localities.—Found in low places, generally in the vicinity of slate or iron ore beds.
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