Flint
Quartz var. Chert (Flint) · Mineral Specimen / Decorative Stone / Industrial Mineral
Crystal System
Trigonal/Hexagonal; Cryptocrystalline (composed of microscopic crystals) with a massive, nodular, or irregular habit.
Mineral Group
Silicates (Tectosilicate)
Chemical Formula
SiO2
Formation Process
Sedimentary/Diagenetic process; typically forms as nodules or masses in limestone or chalk through the accumulation of silica-rich organic remains (like sea sponges or diatoms) that dissolve and reprecipitate.
About This Crystal
An opaque to translucent cryptocrystalline quartz. It typically appears in shades of dark grey, black, or brown with a dull to waxy luster. This specific specimen shows characteristic conchoidal fracture edges and a light-colored outer rind or 'cortex'.
Physical Characteristics
Color: Dark grey/brown; Streak: White; Cleavage: None; Fracture: Conchoidal (shell-like curves); Specific Gravity: 2.6; Fluorescence: Generally none, though some may show faint shades under UV.
Optical Properties
Refractive Index: 1.544-1.553; Isotropic/Uniaxial; Opaque to translucent on thin edges; lacks significant dispersion or pleochroism.
Hardness & Durability
Origin Region
Globally distributed; notable sources include the Chalk formations of England, France (Paris Basin), and various regions in the Midwestern USA.
Hardness & Durability
Mohs Hardness: 7; Toughness: Very high (due to microcrystalline structure); Stable against most chemicals except Hydrofluoric Acid.
Care & Maintenance
Durable and easy to care for; use warm soapy water for cleaning. Store away from softer stones as it can easily scratch them. Resistant to sunlight fading.
Rarity & Value
Common; very low monetary value as a mineral specimen. Value increases moderately if shaped into Neolithic-style tools or artifacts.
Special Characteristics
Produces sparks when struck against steel (triboluminescence); features a conchoidal fracture that allows it to hold an extremely sharp, molecular-level edge.
Lore & History
Historically significant as the primary material for Stone Age tools and weapons. Psychologically used in folklore for protection and grounding; historically used to ignite fires and gunpowder in flintlock firearms.