sedimentary

Chert (Yellow Jasper/Flint)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 Mohs; Color: Ocher, tan, brown; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline; Cleavage: None (Conchoidal fracture); Specific Gravity: 2.6-2.7.

Hardness: 6
Color: Ocher, tan, brown
Luster: Waxy to vitreous

Identified June 18, 2026More sedimentary →

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Physical properties

Hardness: 6.5-7 Mohs; Color: Ocher, tan, brown; Luster: Waxy to vitreous; Crystal Structure: Cryptocrystalline; Cleavage: None (Conchoidal fracture); Specific Gravity: 2.6-2.7.

Formation & geological history

Formed in marine or freshwater environments by the accumulation of siliceous remains of organisms or chemical precipitation. These specimens are often millions of years old and are frequently reshaped by river or glacial action.

Uses & applications

Historically used for stone tools and arrowheads due to sharp edges when fractured. Modernly used in lapidary work, jewelry (tumbled stones), and as decorative filler.

Geological facts

Chert is so hard it can strike sparks from steel. Varieties include Jasper (red/yellow/brown), Flint (dark grey/black), and Agate (banded). This specimen appears to be water-worn and possibly wet, enhancing its color.

Field identification & locations

Identify by its waxy luster, smooth surface, and conchoidal fracture (curving breaks like glass). It is commonly found in riverbeds, gravel pits, and sedimentary rock outcrops globally.