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Offretite & Montmorillonite

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ZLT114531

Offretite & Montmorillonite

Type Locality

Description Tabs

Description
Locality: 
Mont Semiol, Châtelneuf, Loire, Auvergne-Rhône-Alpes, France
Size Range: 
Miniature (4.5-7 cm)
Size: 
2.5 × 4.5 × 3 cm
Description

Prismatic crystals of offretite and spheres of montmorillionite in vugs of the basalt matrix. Good specimen for species and location. Collected in 1981.

Mineral Data
What's on the rock

Offretite

Formula: 
KCaMgAl5Si13O36·16H2O or near
Strunz: 
9.GD.25
Hardness: 
4.0 - 4.5
Type Locality: 
Mont Semiol (Mont Semiouse; Mont Simiouse), Châtelneuf, Saint-Georges-en-Couzan, Loire, Rhône-Alpes, France

Montmorillonite

Formula: 
(Na,Ca)0.33(Al,Mg)2(Si4O10)(OH)2·nH2O
Strunz: 
9.EC.40
Hardness: 
1.0 - 2.0
Streak: 
white
Type Locality: 
Montmorillon, Vienne, Poitou-Charentes, France

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