sedimentary

Chert

Silicon Dioxide (Microcrystalline Quartz)

Hardness: 7 on Mohs scale; Color: Varies from white, grey, beige, to brown; Luster: Waxy to vitreous; Crystal Structure: Microcrystalline/cryptocrystalline; Cleavage: None (exhibits conchoidal fracture); Specific Gravity: 2.60 - 2.65

Hardness: 7 on Mohs scale
Color: Varies from white, grey, beige, to brown
Luster: Waxy to vitreous

Identified August 1, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed by the chemical precipitation of silica from aqueous solutions or the accumulation of siliceous skeletal remains of microscopic organisms like radiolarians and diatoms, typically within limestone or chalk formations over millions of years.

Uses & applications

Historically used for making stone tools, arrowheads, and blades due to its sharp conchoidal fracture; occasionally used in landscaping or decorative gravel.

Geological facts

Chert has been utilized by humans for stone tool manufacture since the Paleolithic era because it flakes in predictable, razor-sharp pieces.

Field identification & locations

Easily identified by its hard conchoidal fracture, waxy luster, and ability to scratch glass. Commonly found weathering out of limestone or chalk cliffs and riverbeds worldwide.

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