A loose, divergent spray of bladed crystals of Hemimorphite from Mexico.
Hemimorphite from Mohina,
Chihuahua, Mexico
CHEMISTRY Zn4(Si2O7)(OH)2 .H2O Hydrous zinc silicate
CRYSTALLOGRAPHY Orthorhombic
CRYSTAL GROWTH AND HABITS Hemimorphite commonly grows as thin, tabular crystals that show hemimorphism (different crystal terminations on either end of the prism form). The crystal clusters grow as fan or sheaf like masses but also as reniform, stalactitic, or fibrous compact masses.
COLOR AND OTHER OPTICAL PROPERTIES Hemimorphite is colorless, white or light green to blue or brown. It is transparent to translucent.
HARDNESS 4.5 - 5
SPECIFIC GRAVITY 3.4 - 3.5
LUSTER Vitreous
STREAK White
BREAKABILITY Hemimorphite has one very good direction of cleavage and 1 that is considered fair. It has an uneven to subconchoidal fracture.
OCCURRENCE Hemimorphite is a secondary mineral found in the oxidized zone of zinc deposits.
ASSOCIATED MINERALS Smithsonite, Sphalerite, Galena, Cerussite, Anglesite, Calcite, Hydrozincite