mineral
Mica
Phlogopite or Biotite group (KMg3(AlSi3O10)(F,OH)2 / K(Mg,Fe)3AlSi3O10(OH)2)
AI-generated identification · may be incorrectHardness: 2.5–3.0 on Mohs scale; Color: Golden-brown to bronze; Luster: Pearly to sub-metallic; Crystal structure: Monoclinic; Cleavage: Perfect basal (peels into thin sheets); Specific gravity: 2.7–3.3
- Hardness
- 2
- Color
- Golden-brown to bronze
- Luster
- Pearly to sub-metallic
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Physical properties
Hardness: 2.5–3.0 on Mohs scale; Color: Golden-brown to bronze; Luster: Pearly to sub-metallic; Crystal structure: Monoclinic; Cleavage: Perfect basal (peels into thin sheets); Specific gravity: 2.7–3.3
Formation & geological history
Formed in igneous environments like pegmatites and metamorphic rocks such as marbles and schists. Phlogopite typically forms through the metamorphism of magnesium-rich limestones and dolomites.
Uses & applications
Used as an electrical insulator, in spark plugs, as an ingredient in joint compound, and in cosmetics to provide shimmer.
Geological facts
Mica sheets were historically used as windows for stoves because they are transparent and can withstand very high temperatures without melting or cracking.
Field identification & locations
Identify by its 'book-like' appearance and ability to peel off paper-thin, flexible flakes with a fingernail. Commonly found in coarse-grained igneous and metamorphic terrains.
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Other mineral specimens
Gneiss or Schist
Gneiss or Mica Schist with Garnet
Metamorphic
Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
Tumbled granite
Granite, a coarse-grained felsic intrusive igneous rock
igneous
Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
metamorphic
Pegmatite with Tourmaline and Quartz
Igneous Pegmatite
igneous
Granite
Granite (Phaneritic intrusive igneous rock)
igneous