sedimentary

Chert (Arrowhead Fragment)

Microcrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 7 (Mohs scale), Color: Variegated levels of white and dark grey, Luster: Waxy to vitreous, Crystal Structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.65

Identified April 10, 2026More sedimentary →

Explore Chert (Arrowhead Fragment) in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed through the accumulation of silica-rich organic remains (such as radiolaria or diatoms) or chemical precipitation from groundwater within limestone or chalk formations. This specimen shows signs of anthropogenic knapping (working by hand).

Uses & applications

Historically used for tools and weapons (arrowheads, scrapers, knives) due to its sharp conchoidal fracture. Modern use in jewelry as 'flint' or 'jasper' and as a common construction aggregate.

Geological facts

Chert was one of the most important minerals for early humans. Its ability to break into sharp, glass-like edges made it the primary material for the Stone Age tool industry. When struck against steel, it produce sparks used for fire starting.

Field identification & locations

Identify by its 'shell-like' curved fractures (conchoidal) and extreme hardness (it will scratch glass). Often found in riverbeds or eroding out of limestone cliffs. Flaked edges suggest it was an ancient tool fragment.