sedimentary

Jasper

Chert (Silica: SiO2)

Hardness: 6.5-7 (Mohs scale), Color: Dark grey to brown with mottled inclusions, Luster: Vitreous to waxy (especially when polished), Crystal Structure: Microcrystalline/Cryptocrystalline, Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.9

Hardness: 6

Identified April 11, 2026More sedimentary →

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Physical properties

Formation & geological history

Jasper forms from the accumulation of silica-rich fluids in volcanic ash or sedimentary environments. Over millions of years, the silica recrystallizes into a hard, dense rock. It is often found in prehistoric river beds or ancient volcanic deposits.

Uses & applications

Used primarily as decorative gemstones, cabochons for jewelry, and as therapy stones. Historically used for making tools due to its conchoidal fracture which creates sharp edges.

Geological facts

Jasper is an opaque variety of chalcedony. The name comes from the Greek word 'iaspis', meaning spotted stone. It has been used as a protective talisman by many ancient civilizations including the Egyptians and Greeks.

Field identification & locations

Identify in the field by its hardness (it can scratch glass), the lack of visible crystals even under magnification, and its smooth, waxy surface when naturally tumbled by water. It is common in gravel pits and beaches.