sedimentary

Chalcedony (Chert/Flint variety)

Silicon Dioxide (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5–7 on Mohs scale; Color: honey-yellow, tan, or grayish; Lustre: waxy to vitreous; Crystal Structure: Cryptocrystalline (hexagonal system); Cleavage: none (conchoidal fracture); Specific Gravity: 2.6–2.64

Hardness: 6
Color: honey-yellow, tan, or grayish

Identified June 20, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed primarily as a sedimentary precipitate from silica-rich fluids in limestone or through the replacement of organic materials. It can also occur in volcanic cavities (geodes).

Uses & applications

Used historically for stone tools and weapons due to its sharp fracture edges. Modern uses include semi-precious jewelry, ornamental lapidary work, and as grinding media in ball mills.

Geological facts

This material was essential to early human civilizations for making arrowheads and spear points. It is essentially a 'microcrystalline' form of quartz where the crystals are too small to see with a standard microscope.

Field identification & locations

Identify in the field by its smooth, shell-like (conchoidal) fracture and waxy surface. Look for it in sedimentary basins or as nodules in limestone. It is harder than steel and will easily scratch glass.