Class: Silicates
A secondary mineral typically found in the oxidised zone of zinc-bearing mineral deposits (
Anthony et al., 2001—2005). Faceted specimens are extremely rare.
Original description: ‘Hemimorphit’ Kenngott, A., 1853. Hemimorphit — Das Mohs’sche Mineralsystem, Verlag und Druck, Wien: 67—68 [
view in ‘Library’].
Type locality: Băiţa mining district, Nucet, Bihor, Romania.
Type material: unknown.
Etymology: in allusion to the mineral’s hemimorphic morphology.
Distribution: Germany: Saxony, Freiberg; Italy: Sardinia; Mexico: large crystals from Santa Eulalia, Chihuahua, and in the Ojuela mine, Mapimí, Durango; Romania: Bihor; Russia: Siberia, Nerchinsk (
Anthony et al., 2001—2005).
Chemistry
Zn4Si2O7(OH)2·H2O
Essential elements: hydrogen (H), oxygen (O), silicon (Si), zinc (Zn).
Crystal data
Crystallography: orthorhombic — pyramidal.
Crystal habit: commonly crystallised, thin tabular, to 10 cm; doubly-terminated crystals show hemimorphism; typically in sheaflike or fan-shaped aggregates (
Anthony et al., 2001—2005).
Optical properties
Colour: colourless, white; pale blue, pale green, grеy, brown from impurities (
Anthony et al., 2001—2005).
Diaphaneity: translucent, transparent in small crystals (
Anthony et al., 2001—2005).
Lustre: vitreous, subpearly, adamantine, rarely silky (
Anthony et al., 2001—2005).
Refractive index: 1.614—1.636 — anisotropic [biaxial (+)] (
Lazzarelli, 2012).
Birefringence: 0.022.
Dispersion: 0.02.
Pleochroism: none (
Arem, 1987: 111).
Material from ‘Repository’
