2. Carbonate of Copper.
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.