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Chamosite with Natrolite
SILICATES; PHYLLOSILICATES; CHLORITE GROUP · MONOCLINIC

Chamosite

(Fe2+,Mg)5Al2Si3O10(OH)8

Hardness
2.5–3
Streak
White
Spec. Gravity
3–3.4
System
Monoclinic

About

Chamosite is a member of the Chlorite, and it forms a series with the mineral Clinochlore. Chamosite is the iron rich end member, and Clinochlore is the magnesium-rich end member. Their properties are very similar, and they are difficult to distinguish from each other, though Chamosite is harder, heavier, and usually less transparent than Clinochlore.

Crystal Forms & Aggregates

Other ID Marks

Larger crystals and masses may have a slightly greasy feel.

Striking Features

Environment

Polymorphs

Noteworthy Localities

Chamosite is more common then perceived, but it usually is just in small uninteresting flakes labelled as Chlorite without being specifically identified. Specific occurences include the Yaogangxian Mine, Hunan Province, China; Klenovec, Slovakia; Ashland, Middlesex Co., Massachusetts; Washington Pass, Okanogan Co., Washington; Atlantic City, Fremont Co., Wyoming; and Moat Mountain, Carroll County, New Hampshire. The New Jersey traprock quarries of Paterson and Prospect Park, Passaic Co., and the Milington Quarry, Somerset  Co. contain Chamosite coatings and dustings upon other minerals.

Common Mineral Associations

Distinguishing Similar Minerals

Photos

Crystal forms

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Assymetrical Pseudohexagon