Large Black Mica Rough Freeform Specimen - 150mm, 1.45Kg

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Large Black Mica Rough Freeform Specimen – 150mm, 1.45kg

A commanding display piece, this large rough freeform black mica specimen measures approximately 150mm and weighs a substantial 1.45kg. Its deeply lustrous, layered surfaces catch the light with an almost metallic shimmer, making it an impressive addition to any mineral collection, shelf display, or study. The natural freeform shape preserves the raw character of the material exactly as it formed within the earth.

Physical Properties

• Black Mica (Biotite) — Chemical formula: K(Mg,Fe)₃(AlSi₃O₁₀)(OH)₂ | Hardness: 2.5–3 Mohs | Crystal system: Monoclinic | Lustre: Vitreous to submetallic | Transparency: Opaque to subtranslucent on thin edges | Colour: Deep black to dark brown-black

Geology & Formation

Biotite mica forms as a primary mineral in igneous rocks such as granite and diorite, as well as in metamorphic rocks including schist and gneiss. It crystallises during the cooling of magma or under high-pressure, high-temperature metamorphic conditions, often growing in distinctive book-like or platy masses. The black colouration results from elevated iron and magnesium content within its layered silicate structure. Large, well-defined specimens of this size are typically sourced from pegmatite intrusions, where slow cooling allows crystals to grow to impressive dimensions.

Crystal Properties

Black mica is associated with grounding, protection, and energetic shielding. It is said to help deflect negativity, support emotional resilience, and anchor scattered energy — making it a valued stone for those seeking stability and clarity amid change. Its reflective surfaces are also linked to self-reflection and inner truth.

Specimen Details

• Weight: 1.45kg
• Size: Approximately 150 x 89 x 75mm
• Type: Rough freeform specimen
• Mineral: Black Mica (Biotite)
• Origin: Brazil