Hydrozincite - Encyclopedia

Class : Carbonates, nitrates, borates
Subclass : Hydrated carbonates
Crystal system : Monoclinic
Chemistry : Zn₅(CO₃)₂(OH)₆
Rarity : Quite common

Hydrozincite is a hydrated carbonate formed in an arid climate in the oxidation zone of zinc deposits. Its name is derived from its chemical composition : a hydrated zinc carbonate. It is rare in small crystals, acicular to lamellar, colorless and transparent, rarely exceeding a millimeter, lining geodes and cracks in karst cavities. Hydrozincite usually occurs in concretionary crusts with a fibrous texture, in earthy or chalky masses with a stalactitic, pisolitic or kidney-shaped appearance. It has a white, gray, yellowish color ; it is sometimes colored brownish or reddish by iron oxides. It constitutes a locally important secondary zinc ore.

Main photo : Hydrozincite from Andara mining district, Camaleño, Spain © Michael Shaw

Hydrozincite from Mehdi Abad Mine, Bafq, Yazd Province, Iran © Eugene & Sharon Cisneros

Hydrozincite from Guiyang, Guizhou, China © Rob Lavinsky

Hydrozincite from San Rafael Mine, Nevada, USA © Robert Meyer

Blue hydrozincite from LEs Malines, Gard, France

Hydrozincite in the World

The most beautiful crystallized groups come from the Chah-Huh zinc deposit (Iran). These are fine transparent crystals which lined an immense geode of several tens of cubic meters. This oxidation zone geode opened into a massive hydrozincite zone, exploited as ore. Hydrozincite was also very abundant and exploited in the Comillas deposit, near Santander (Spain), which also provided some beautiful millimeter crystals. It is also abundant in Mexico (Mapimi), and in numerous American (Nevada, New Mexico, Utah) and Chinese (Guizhou, Zhejiang and Yunnan) deposits in sometimes decimetric concretions.

Hydrozincite in France

In France, hydrozincite is reported in numerous occurrences, notably in Malines (Gard) where it can be blue due to aurichalcite inclusions, in the Oms sector (Pyrénées-Orientales), in Chessy (Rhône), etc...

Twinning

Twins are known but not externally identifiable.

Fakes and treatments

No fakes recorded for this mineral species, but can easily be confused with other carbonates without chemical analyses.

Hardness : 2 to 2.5
Density : 3.5 to 4
Fracture : Irregular
Streak : White

TP : Translucent to transparent
RI : 1.630 to 1.750
Birefringence : 0.120
Optical character : Biaxial -
Pleochroism : None
Fluorescence : Blue

Solubility : Nitric acid, hydrochloric acid

Magnetism : NoneRadioactivity : None

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