mineral

Quartz with Chalcedony

Silicon dioxide (SiO2)

Hardness: 7 (Mohs scale), Color: White, tan, and creamy-brown, Luster: Vitreous to waxy, Crystal structure: Trigonal/Microcrystalline, Cleavage: None/Conchoidal fracture, Specific gravity: 2.65

Identified April 3, 2026More mineral →

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Physical properties

Hardness: 7 (Mohs scale), Color: White, tan, and creamy-brown, Luster: Vitreous to waxy, Crystal structure: Trigonal/Microcrystalline, Cleavage: None/Conchoidal fracture, Specific gravity: 2.65

Formation & geological history

Formed from hydrothermal solutions or the cooling of silica-rich fluids. Often found in volcanic cavities (geodes) or as vein fillings in various rock types, ranging from the Precambrian to Holocene eras.

Uses & applications

Used primarily for crystal collecting, as decorative stones, or in the manufacturing of glass and ceramics if found in high purity. Also historically used for making stone tools due to its hardness.

Geological facts

Quartz is the second most abundant mineral in Earth's continental crust. Chalcedony is its cryptocrystalline relative, meaning the crystals are so small they can only be seen under extreme magnification.

Field identification & locations

Identify in the field by its inability to be scratched by a steel knife (7 on Mohs scale), its waxy translucent edges, and glassy interior. Common in desert environments and stream beds.