Pegmatite with Quartz and Biotite
Igneous Rock / Pegmatite Matrix with Quartz and Mica · Mineral Specimen
Crystal System
Varies by mineral component; Quartz is Trigonal, Biotite is Monoclinic
Mineral Group
Silicates (Tectosilicates and Phyllosilicates)
Chemical Formula
SiO2 (Quartz) with complex silicate matrix (K(Mg,Fe)3AlSi3O10(OH)2 for Biotite)
Formation Process
Igneous process, specifically late-stage crystallization of granitic magma forming pegmatites under high water-vapor pressure
About This Crystal
The specimen exhibits a dark, finely crystalline or micaceous matrix interspersed with distinct, irregular white quartz pockets and translucent to milky crystalline aggregates, showing contrasting dark and light textures with vitreous to submetallic luster in the dark mineral components
Physical Characteristics
Color ranges from deep black/dark grey to stark white; streak is white for quartz and grey-white for mica; uneven to conchoidal fracture; specific gravity typically ranges around 2.6 to 2.8 g/cm3; brittle tenacity
Optical Properties
Quartz is uniaxial positive with low birefringence; biotite is strongly pleochroic under microscopic examination; aggregate structure shows no unified optical phenomenon like chatoyancy or play of color
Hardness & Durability
Origin Region
Found globally in continental crustal environments, notably in pegmatite fields such as Minas Gerais, Brazil, and various locations in North America and Madagascar
Hardness & Durability
Mohs hardness varies by component: Quartz is 7, Mica is 2.5 to 3; overall durability depends on the specific mineral grain, making it moderate for display specimens but unsuitable for delicate jewelry without setting
Care & Maintenance
Clean with mild soapy water and a soft brush; avoid harsh acids or prolonged soaking; store safely to prevent scratching softer components against harder mineral specimens
Rarity & Value
Common; value is generally low to moderate, determined primarily by aesthetic contrast, size, and uniqueness of the mineral association as a raw educational or display specimen
Special Characteristics
Presents as a natural host rock or matrix sample, highlighting mineral juxtaposition and crystallization within a primary igneous environment
Lore & History
Used by mineral collectors for educational and decorative purposes; in modern metaphysical practices, matrix stones are traditionally believed to provide grounding energies and a connection to the stabilizing forces of the earth, though these are strictly non-scientific beliefs