Mineral / Sedimentary

Quartz / Chert

Silicon Dioxide (SiO2)

Hardness: 7 (Mohs scale); Color: White, gray, or translucent; Luster: Vitreous to waxy; Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Hardness: 7 (Mohs scale)
Color: White, gray, or translucent
Luster: Vitreous to waxy

Identified April 4, 2026More mineral / sedimentary →

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Physical properties

Hardness: 7 (Mohs scale); Color: White, gray, or translucent; Luster: Vitreous to waxy; Crystal structure: Trigonal/Hexagonal; Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Formation & geological history

Formed through the accumulation of silica-rich fluids in rock cavities or the precipitation of microscopic silica organisms in marine environments. Can occur across all geological ages from Precambrian to recent.

Uses & applications

Used in glass manufacturing, electronics (as piezoelectric crystals), abrasives, and as semi-precious gemstones in jewelry. Chert specifically was historically used for stone tools.

Geological facts

Quartz is the second most abundant mineral in Earth's continental crust. When microcrystalline and opaque, it is often called chert or jasper; when translucent, it is often called chalcedony.

Field identification & locations

Identify in the field by its hardness (it will scratch glass), its lack of cleavage, and its characteristic shell-like (conchoidal) fracture pattern. Commonly found in riverbeds, fields, and mountainous outcrops.