Hydrous phyllosilicate that exfoliates dramatically when heated, expanding up to 30 times its original volume. Color: Brown, golden brown, greenish. Luster: Vitreous to pearly. Streak: White to yellowish. Cleavage: Perfect basal. Hardness: 1.5-2. Transparency: Translucent to opaque. Crystal system: Monoclinic. Chemical formula: Mg,Fe,Al ₃ Al,Si ₄O₁₀ OH ₂·4H₂O. Specific gravity: 2.4-2.7. Formation: Forms from weathering or hydrothermal alteration of biotite and phlogopite micas. Common geological settings: South Africa, USA, Brazil, China; found in weathered ultramafic and mafic rocks. Common look-alikes and related entries: Biotite, Phlogopite, Chlorite.
These authoritative resources support category-level nomenclature, terminology, identification methods, and safety. When a specimen-specific safety warning appears, the public-health source listed here directly supports that precaution. They are not line-by-line citations for every other property on this entry, and natural specimens vary.
Editorial owner
GeoMiner
Last updated
2026-03-30T14:36:53.054696+00:00
Review status
Published; not independently peer-reviewed
IMA–CNMNC List of Mineral Names — International Mineralogical Association. Official mineral-name, nomenclature, and classification records.
Mineral ID Key — Mineralogical Society of America. Physical-property identification methods, repeat-testing guidance, and limitations.
Hydrous phyllosilicate that exfoliates dramatically when heated, expanding up to 30 times its original volume.
How can you identify Vermiculite?
Compare several properties rather than relying on colour alone. This entry records colour: Brown, golden brown, greenish; lustre: Vitreous to pearly; streak: White to yellowish; Mohs hardness: 1.5-2; cleavage: Perfect basal; crystal system: Monoclinic; transparency: Translucent to opaque. Confirm an important identification with additional field tests or qualified laboratory work.
How does Vermiculite form?
Forms from weathering or hydrothermal alteration of biotite and phlogopite micas.
Where is Vermiculite commonly found?
South Africa, USA, Brazil, China; found in weathered ultramafic and mafic rocks.
What is Vermiculite commonly confused with?
Vermiculite may be confused with Biotite, Phlogopite, Chlorite. Compare multiple diagnostic properties because colour and surface appearance can overlap.
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