etallic.
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 lustre, 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
arsenical 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. Lustre, metallic. Occurs usually massive and very
arborescent. Before the Bp. on Ch. it fuses, and if the heat is
sufficiently high it assumes 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, brass-yellow, often golden-yellow. Lustre, metallic.
Occurs crystallized, but is generally found massive. 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 masses. 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 masses, often very
shining. 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 wi