Part 7 (1/2)

~Smalt.i.te~, Co(Fe, Ni) As_{2}, Co . 28, As . 72.--H = 5.5, G = 6.37-7.30.

Color, tin-white or steel-gray. l.u.s.tre, metallic. When heated to redness in an ignition tube it yields a sublimate of metallic a.r.s.enic. Before the Bp. on Ch. it fuses readily, with emission of a.r.s.enical fumes, to a grayish black magnetic globule. This globule may be examined for iron, cobalt, and nickel with the borax bead.

~Cobalt.i.te~, CoS_{2} + CoAs_{2}, Co . 36, As . 45, S . 19.--H = 5.5, G = 6.0-6.3. Color, silver-white tinged with red. Metallic l.u.s.tre. Before the Bp. on Ch. fuses easily, with emission of copious a.r.s.enical fumes, to a gray magnetic globule. Remains unchanged in the ignition tube.

~Linnaeite~, (Co, Ni)_{3}S_{4}, (Co, Ni)58, S . 42.--H = 5.5, G = 4.8-5.0.

Color, bright steel-gray, sometimes reddish. l.u.s.tre, metallic.

Crystallizes in the regular octahedron. Before the Bp. on Ch. fuses to a metallic globule which is attracted by the magnet. With borax bead gives reaction for cobalt.

~Erythrite~, Co_{3}O_{8}As_{2} + 8 H_{2}O, As_{2}S_{5} . 38.4, CoO . 37.6, H_{2}O . 24.0.--

H = 1.5-2.0, G = 2.95.

Color, crimson to peach-red. When crystallized, of pearly l.u.s.tre, but frequently dull and earthy. Heated in ignition tube gives off water, and color changes to blue or green. Before the Bp. on Ch. in R. F. it emits a.r.s.enical fumes and melts to a dark gray globule which with the borax bead reacts for cobalt.

ORES OF COPPER

~Native Copper, Cu.~--

H = 2.5-3, G = 8.5-8.9.

Color, copper-red. l.u.s.tre, metallic. Occurs usually ma.s.sive and very arborescent. Before the Bp. on Ch. it fuses, and if the heat is sufficiently high it a.s.sumes a bright bluish-green surface; on cooling it is covered with a coat of black oxide. In the borax bead it reacts for copper.

~Chalcopyrite~, CuFeS_{2}, Cu . 35, Fe . 30, S . 35.--H = 3.5-4, G = 4.1-4.3. Color, bra.s.s-yellow, often golden-yellow. l.u.s.tre, metallic.

Occurs crystallized, but is generally found ma.s.sive. Is easily scratched with a knife. Heated in an ignition tube decrepitates, and occasionally yields a faint sublimate of sulphur. Before the Bp. on Ch.

it blackens, but becomes red again on cooling. Before the Bp. on Ch.

with Na_{2}CO_{3} and KCN it is reduced, and the metals are obtained in separate ma.s.ses. It reacts with the borax bead for copper and iron.

~Copper Glance~, Cu_{2}S, Cu . 80, S . 20.--H = 2.5-3.0, G = 5.5-5.8.

Color, dark blue to steel-gray. Occurs in compact ma.s.ses, often very s.h.i.+ning. Before the Bp. on Ch. fuses to a globule which boils and emits glowing drops. Sulphur dioxide escapes abundantly, and the outer flame is colored blue. Before the Bp. on Ch. with Na_{2}CO_{3} yielding a metallic globule.

~Tetrahedrite~, 4 CuS + Sb_{2}S_{3}.--Frequently contains silver, iron, mercury, and zinc. H = 3.0-4.0, G = 4.5-5. Color, steel-gray to iron-black. Heated in an ignition tube fuses and gives a sublimate of antimonious oxide. When mercury is present this condenses in the upper part of the tube, forming the characteristic mirror. Before the Bp. on Ch. it fuses readily to a metallic globule, emitting dense white fumes; zinc and antimony coatings are deposited on the Ch. After long ignition before the Bp., if the mineral is finely powdered and mixed with Na_{2}CO_{3} and KCN, the ore is reduced to the metal.

~Cuprite~, Cu_{2}O, Cu . 89, O . 11.--

H = 3.5-4.0, G = 5.5-6.15.

Color, intense crimson-red. Before the Bp. on Ch. blackens and fuses quietly, and finally yields a metallic globule of copper. Before the Bp.

on Ch. with Na_{2}CO_{3} and KCN it is easily reduced.

~Malachite~, 2 CuO + CO_{2} + H_{2}O, CuO . 72, CO_{2} . 20, H_{2}O . 8.--