~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.-- H = 3.5-4.0, G = 3.90-4.03. Color, bright green. Occurs generally in mammillated concretions. Lustre, shining and fracture, silky. Heated in an ignition tube yields water and blackens. Before the Bp. on Ch. it fuses to a metallic globule. Before the Bp. on Ch. with Na_{2}CO_{3} and KCN it is easily reduced. With borax bead gives characteristic coloration. ~Azurite~, 3 CuO + 2 CO_{2} + H_{2}O, CuO . 69, CO_{2} . 26, H_{2}O . 5.-- H = 3.5-4.0, G = 3.77-3.83. Color, azure-blue. Occurs usually in crystallized or globular masses. Lustre, earthy or vitreous. Before the Bp. and with other reagents behaves like malachite. ~Chrysocolla~, CuO + SiO_{2} + 2 H_{2}O, SiO_{2} . 34.2, CuO . 45.3, H_{2}O . 20.5.--H = 2.0-3.0, G = 2. Color, bluish-green, closely resembling malachite. Occurs usually as an incrustation, its surface being very smooth, like enamel. In an ignition tube it blackens and yields water. Before the Bp. on Ch. in O. F. it blackens, coloring the flame bright green; in the R. F. it turns red. Before the Bp. on Ch. with Na_{2}CO_{3} yields metallic copper. In borax bead it reacts for copper. ~Atacamite~, CuCl_{2} + 3 CuO_{2}H_{2}--Cl . 16.6, O . 20.3, Cu . 50.1, H_{2}O . 13.0.-- H = 3.0-3.5, G = 3.75-3.77. Color, green to blackish green. Lustre, adamantine to vitreous. In an ignition tube yields water. Before the Bp. on Ch. colors flame blue. Before the Bp. on Ch. with Na_{2}CO_{3} and KCN is reduced to the metal. In borax bead it reacts for copper. ORES OF IRON ~Limonite~, 2 Fe_{2}O_{3} + 3 H_{2}O, Fe_{2}O_{3} . 86, H_{2}O . 14.--H = 5.0-5.5, G = 3.6-4.0. Color, brown to ochre-yellow. Earthy or semi-metallic in appearance. In an ignition tube yields water. Before the Bp. on Ch. infusible. In borax bead reacts for iron. ~Hematite~, Fe_{2}O_{3}, Fe . 70, O . 30.-- H = 5.5-6.5, G = 4.9-5.3.