Stannite, 2 Cu2S . SnS2 + 2 (FeS . ZnS) Sn . S2.—H = 4.0, G = 4.3-4.5. Color, steel-gray to iron-black. Lustre, metallic. Occurs usually massive and disseminated. Heated in an ignition tube it yields sulphur dioxide. Before the Bp. on Ch. it emits sulphur dioxide and becomes covered with oxide of tin. Before the Bp. on Ch. with Na2CO3 and KCN it gives an impure globule of copper. A very difficult mineral to determine.
Ores of Zinc
Calamine, H2Zn2O5Si, SiO2 . 25.0, ZnO . 67.5, H2O . 7.5.—H = 4.5-5.0, G = 3.4-3.5. Color, white, gray, bluish, or brown. Lustre, vitreous. Brittle. In an ignition tube yields water when heated and becomes milky white. Before the Bp. on Ch. practically infusible. With Co(NO3)2 it assumes a green color which passes into a fine blue when the heat is increased.
Smithsonite,
Zn . CO3, ZnO . 64.8, CO2 . 35.2.—
H = 5, G = 4.30-4.45. Color, gray, yellow, brown, and green. Lustre, vitreous, pearly. Heated in an ignition tube CO2 is evolved, residue appearing white. It often contains impurities of Cd, Pb, Fe, Mn, Ca, and Mg. When these are present the residue in the ignition tube becomes dark on cooling. Before the Bp. on Ch. with Na2CO3 and exposed to the R. F. it is decomposed. It gives the characteristic reaction for zinc with Co(NO3)2.
Zincite, ZnO, Zn . 80.3, O . 19.7—
H = 4.0-4.5, G = 5.43-5.70.
Color, blood-red. Lustre, brilliant, subadamantine. Before the Bp. on Ch. infusible. Before the Bp. on Ch. with Na2CO3 gives coating of zinc oxide. Gives characteristic reaction with Co(NO3)2. It frequently contains a small quantity of Mn2O3, which may be detected in the borax bead.
Sphalerite, ZnS, Zn . 67, S . 33.—