Chlorite
Chlorite group
Common · (Mg,Fe)₃(Si,Al)₄O₁₀(OH)₂·(Mg,Fe)₃(OH)₆
A phyllosilicate group forming during low-grade metamorphism and hydrothermal alteration. Its green comes mostly from iron, and the purest magnesian clinochlore can be almost white. Commonly found coating fractures and replacing amphiboles, pyroxenes and biotite in altered igneous rocks.
Identity
- Formula
- (Mg,Fe)₃(Si,Al)₄O₁₀(OH)₂·(Mg,Fe)₃(OH)₆
- Chemical class
- Silicate
- Members
- Clinochlore, Chamosite, Cookeite
Crystallography
- Crystal system
- Monoclinic
- Habits
- Foliated, Massive, Granular
- Fracture
- Uneven
Physical properties
- Mohs hardness
- 2.5
- Density
- 2.65 g/cm³
- Luster
- Pearly, Dull
- Colors
- green, dark green, olive green, black, white
- Streak
- white to pale green
- Transparency
- Translucent, Opaque
Geology
- Origins
- Metamorphic, Hydrothermal
- Host rocks
- Volcanic rock, Schist and gneiss
- Associated minerals
- Quartz, Actinolite, biotite, Calcite
- Found in
- Garnierite, Schist, Slate, Soapstone
- Geography
- worldwide
Classification
- Rarity
- Common
- Gem quality
- No
Sources
- Chlorite. Mindat.org (Hudson Institute of Mineralogy).
- M. Pasero and others, IMA Commission on New Minerals, Nomenclature and Classification, The New IMA List of Minerals, updated September 2026. International Mineralogical Association (CNMNC), 2026.
- J. W. Anthony, R. A. Bideaux, K. W. Bladh, M. C. Nichols, Clinochlore. Mineral Data Publishing, Handbook of Mineralogy, 2001.
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