A. _Azurite_; kupferlazur. Blue. Crystallizes in oblique rhomboidal
prisms; specific gravity 3 to 3·83; scratches calc-spar, is scratched by
fluor; yields water with heat, and blackens. Its constituents are,
carbonic acid 25·5; oxide of copper 69·1; water 5·4. The Chessy and
Banat azurite is most profitably employed to make sulphate of copper.
B. _Malachite_; green carbonate or mountain green. Crystallizes in right
rhomboidal prisms; specific gravity 3·5; affords water with heat, and
blackens. It consists of carbonic acid 18·5; oxide of copper 72·2; water
9·3.
C. _Mysorine_; anhydrous carbonate of copper. Dark brown generally
stained green or red; conchoidal fracture; soft, sectile; specific
gravity 2·62. It consists of carbonic acid 16·7; oxide of copper 60·75;
peroxide of iron 19·5; silica 2·10. This is a rare mineral found in the
Mysore.
3. _Chromate of Copper and Lead_; vauquelinite. Green of various shades;
specific gravity 6·8 to 7·2; brittle; scratched by fluor; fusible at the
blowpipe with froth and the production of a leaden bead. It consists of
chromic acid 28·33; oxide of lead 60·87; oxide of copper 10·8. It occurs
at Berezof in Siberia along with chromate of lead.
4. _Dioptase_; silicate of copper; emerald copper. Specific gravity 3·3;
scratches glass with difficulty; affords water with heat, and blackens;
infusible at the blowpipe. It consists of silica 43·18; oxide of copper
45·46; water 11·36. This rare substance comes from the government of
Kirgis.
The silicate of Dillenberg is similar in composition.
5. Gray copper ore called Panabase, from the number of metallic bases
which it contains; and Fahlerz. Steel gray; specific gravity 4·79 to
5·10; crystallizes in regular tetrahedrons; fusible at the blowpipe,
with disengagement of fumes of antimony and occasionally of arsenic;
swells up and scorifies, affording copper with soda flux. Is acted upon
by nitric acid with precipitation of antimony; becomes blue with
ammonia; yields a blue precipitate with ferrocyanide of potassium; as
also indications frequently of zinc, mercury, silver, &c. Its
composition which is very complex is as follows: sulphur 26·83; antimony
12·46; arsenic 10·19; copper 40·60; iron 4·66; zinc 3·69; silver 0·60.
Some specimens contain from 5 to 31 per cent. of silver. The gray copper
ores are very common; in Saxony; the Hartz; Cornwall; at Dillenberg; in
Mexico; Peru, &c. They are important on account both of their copper and
silver. _Tennantite_ is a variety of Fahlerz. It occurs in Cornwall. Its
constituents are, sulphur 28·74; arsenic 11·84; copper 45·32; iron 9·26.
6. _Hydrated silicate of Copper_; or Chrysocolla. Green or bluish green;
specific gravity 2·03 to 2·16; scratched by steel; very brittle; affords
water with heat, and blackens; is acted upon by acids, and leaves a
siliceous residuum. Solution becomes blue with ammonia. Its constituents
are silica 26; oxide of copper 50; water 17; carbonic acid 7.
7. _Muriate of Copper._ Atakamite; green; crystallizes in prisms;
specific gravity 4·43. Its constituents are, chlorine 15·90; copper
14·22; oxide of copper 54·22; water 14·16; oxide of iron 1·50. The green
sand of Peru, collected by the inhabitants of Atakama, is this substance
in a decomposed state.