Clear Quartz
Quartz var. Rock Crystal · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Trigonal (Hexagonal sub-system); usually hexagonal prisms terminated by two rhombohedrons. In its rough, fractured state as shown, it displays conchoidal fracture rather than crystal faces.
Mineral Group
Silicates (Tectosilicate subgroup)
Chemical Formula
SiO2
Formation Process
Hydrothermal or Igneous; crystallizes from silica-rich fluids in rock cavities or during the cooling of magma in pegmatitic environments.
About This Crystal
Transparent, colorless specimen with a vitreous (glass-like) luster. It exhibits distinctive conchoidal (shell-like) fractures and sharp edges, typical of a broken fragment of macrocrystalline quartz. The surface shows some internal reflections and small white inclusions near the base.
Physical Characteristics
Color: Colorless; Streak: White; Cleavage: None (indistinct); Fracture: Conchoidal; Specific Gravity: 2.65; Tenacity: Brittle; Fluorescence: Generally inert.
Optical Properties
Refractive Index: 1.544-1.553; Birefringence: +0.009; Optically Uniaxial (+); Displaying high transparency with no pleochroism.
Hardness & Durability
Origin Region
Found globally; notable sources include Minas Gerais, Brazil; Arkansas, USA; and Madagascar. Forms in hydrothermal veins and pegmatites.
Hardness & Durability
Mohs Hardness: 7; Toughness: Fair (due to lack of cleavage); Stability: Very stable, resistant to most household chemicals except hydrofluoric acid.
Care & Maintenance
Clean with warm soapy water and a soft brush. Ultrasonic and steam cleaning are generally safe unless internal fractures are present. Store separately to avoid scratching softer materials.
Rarity & Value
Abundant/Common. Value is determined by clarity and size. Rough specimens are inexpensive; high-clarity faceted stones or large points are more valuable. Highly susceptible to synthetic imitation and lab-growth.
Special Characteristics
Piezoelectric (generates electricity under pressure) and Pyroelectric. Note the conchoidal fracture pattern which distinguishes it from glass (which has similar fractures but typically contains air bubbles).
Lore & History
Known as the 'Master Healer' in metaphysical traditions. Historically used by the Ancient Greeks who believed it was 'everlasting ice' (krystallos). Used for tool making in the Neolithic and as divining spheres in various cultures.