Gneiss containing Quartz and Mica
Metamorphic Rock: Gneiss with Quartz (SiO2) and Biotite/Muscovite Mica · Mineral Specimen / Metamorphic Rock
Crystal System
Varies by mineral content: Quartz is Trigonal (hexagonal prisms), Micas are Monoclinic (tabular/platy)
Mineral Group
Silicates (Tectosilicates and Phyllosilicates)
Chemical Formula
SiO2 (Quartz) + K(Mg,Fe)3AlSi3O10(OH)2 (Biotite) + KAl2(AlSi3O10)(OH)2 (Muscovite)
Formation Process
Metamorphic: High grade regional metamorphism under high temperature and pressure, causing recrystallization and foliation
About This Crystal
A coarse-grained metamorphic rock showing distinct banding or a mottled appearance of white/grey quartz and dark/earthy micas. Luster varies from vitreous on quartz surfaces to pearly/sub-metallic on mica flakes. Translucency is low to opaque.
Physical Characteristics
Color is a mix of white, grey, brown, and black. Streak is white. Shows metamorphic foliation (layering). Specific gravity is approx 2.6-2.9. Quartz components are brittle with conchoidal fracture.
Optical Properties
Generally opaque in bulk. Quartz is uniaxial positive with low birefringence; Mica shows high birefringence in thin section but is mostly opaque/shiny in hand samples.
Hardness & Durability
Origin Region
Found globally in many regions including the Appalachian Mountains (USA), Scandinavia, and India
Hardness & Durability
Variable: Quartz (Mohs 7) is very durable, but Mica (Mohs 2-3) is soft and can flake or peel along cleavage planes.
Care & Maintenance
Clean with warm soapy water and a soft brush. Avoid ultrasonic cleaners as the layered structure may separate. Store away from harder gems to prevent scratching of the mica components.
Rarity & Value
Extremely Common; primarily valued as a geological specimen or for use as decorative building stone rather than a gemstone.
Special Characteristics
Displays distinct 'gneissose' banding and texture; mica flakes provide a characteristic shimmering or 'glinting' effect when rotated under light.
Lore & History
Historically used for construction and carving due to its abundance and durability. In lore, it is often associated with grounding, perseverance, and seeing the 'big picture' during times of transformation.