Hectorite

hectorite

clinoptilolite

bentonite

saponite

Images

Formula: Na_0.3(Mg,Li)₃Si₄O₁₀(F,OH)₂.nH₂O
Phyllosilicate (sheet silicate), smectite group, lithium-bearing mineral
Crystal System: Monoclinic
Specific gravity: 2.3 measured
Hardness: 1 to 2
Streak: White
Colour: White
Solubility: Decomposed or gelatinised by common acids
Common impurities: Ti,Al,Fe,Ca,K,Cl
Environments

Volcanic igneous environments
Hot spring deposits

Hectorite is a clay mineral formed from altered volcanic tuff ash with a high silica content and related to hot spring activity (Webmin). It has been found in an alteration of clinoptilolite in bentonite in an alkaline lake environment and can be admixed with saponite; it usually contains minor fine grained calcite, and it is also found in argillaceous skarn (Dana).

Localities

At Puy Chalard, near Vertaizon, Clermont-Ferrand, Puy-de-Dôme, Auvergne-Rhône-Alpes, France, hectorite occurs with calcite veins in acid tuff (Dana).

At the type locality, the Hector Bentonite Mine No. 1, Hector, Cady Mountains, San Bernardino county, California, USA, hectorite occurs in a bentonite deposit, altered from clinoptilolite derived from volcanic tuff and ash with a high glass content, related to hot spring activity. Associated minerals include calcite and clinoptilolite (HOM).

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