mineral
Mica (likely biotite-rich mica aggregate)
Biotite, a potassium–iron–magnesium mica; approximate formula K(Mg,Fe)₃AlSi₃O₁₀(F,OH)₂
AI-generated identification · may be incorrectBrown, shiny, flaky sheets with perfect basal cleavage and a platy, layered structure; Mohs hardness about 2.5–3. The small specimen’s exact mineral identity cannot be confirmed from the image alone.
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Physical properties
Brown, shiny, flaky sheets with perfect basal cleavage and a platy, layered structure; Mohs hardness about 2.5–3. The small specimen’s exact mineral identity cannot be confirmed from the image alone.
Formation & geological history
Mica forms in igneous and metamorphic rocks as magma cools or during recrystallization under heat and pressure; biotite is found in rocks spanning a wide range of geological ages.
Uses & applications
Mica is used as an electrical and thermal insulator, in fillers and cosmetics, and as a collector specimen; this small piece is mainly of educational or decorative interest.
Geological facts
Mica’s layers split into thin, flexible sheets, a property that made it useful in early electrical equipment and stove windows.
Field identification & locations
The glittering brown plates and sheet-like cleavage suggest mica; biotite commonly occurs in granite, schist, and gneiss worldwide. Confirming biotite rather than another mica requires closer examination.
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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