Hydrozincite, as a white powder crusting brown-coloured drusy hemimorphite, has been analyzed., The Sample was obtained from the Nakatatsu Mine, Fukui Prefecture, one of the famous zinc-lead mines in Japan., It consists, under the microscope, of minute fibrous crystals, lining perpendicular to the surface of the crust., The optical properties are : straight extinction, elongation positive, possibly biaxial negative, with α=1., 649, γ=1., 704, Sp., gr., 3., 59 (26°C)., The result of the chemical analysis follows : ZnO 66., 70%, CaO 2., 69, Al
2O
3 1., 17, Fe
2O
3 tr., CO
2 16., 26 Insol., 0., 26, H
2O (+) 11., 75, H
2O(-) 1., 55, Total 100., 38., These may be expressed by the formula Zn
5(CO
3)
2(OH)
6·H
2O., An X-ray powder photograph taken with Cu K
α compares favorably with that of hydrozincite from Deming, New Mexico.,
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