Massive Gray Quartz (Rock Crystal)
Quartz var. Gray Quartz (SiO2) · Mineral Specimen / Decorative Stone
Crystal System
Trigonal/Hexagonal; exhibiting a massive, granular, and microcrystalline habit with no visible external crystal faces in this specimen.
Mineral Group
Silicates (Tectosilicate group)
Chemical Formula
SiO2 (Silicon Dioxide) with possible traces of aluminum and iron
Formation Process
Primarily Hydrothermal or Igneous; forms via the cooling of silica-rich magma or precipitation from hot, silica-saturated fluids in veins and crustal voids.
About This Crystal
A dense, massive gray specimen with a matte to waxy luster. The surface is grainy and uneven, showing a range of light to slate gray tones with small, scattered white inclusions or surface weathering crusts (cortical material).
Physical Characteristics
Color: Gray to light charcoal; Streak: White; Cleavage: None; Fracture: Conchoidal to irregular; Specific Gravity: 2.65; Tenacity: Brittle; Fluorescence: Generally none.
Optical Properties
Refractive Index: 1.544–1.553; Birefringence: 0.009; Optically Uniaxial (+); Transparency: Opaque to translucent on thin edges; Luster: Vitreous to dull/earthy when unpolished.
Hardness & Durability
Origin Region
Worldwide; commonly found in mountainous regions such as the Appalachian Mountains (USA), the Alps (Europe), and the Brazilian Highlands.
Hardness & Durability
Mohs Hardness: 7; Toughness: Fair (brittle); Stability: Excellent against most chemicals except hydrofluoric acid; Very durable for jewelry and decor.
Care & Maintenance
Safe to clean with warm soapy water and soft brushes. Highly stable; not sensitive to sunlight, though extreme thermal shock should be avoided.
Rarity & Value
Common; Value is generally low as a raw specimen, valued mostly for industrial use or as basic landscaping/bulk decorative material.
Special Characteristics
Microcrystalline texture; lacking the transparency of 'Rock Crystal' quartz; may exhibit slight sparkles from tiny internal cleavage planes of individual grains.
Lore & History
Historically used for tool-making (lithics) due to its hardness and predictable fracture. In traditional lore, gray quartz is associated with grounding, stability, and neutralizing negative environmental energy.