Chert (Jasper/Agate variety)

Physical Properties

Hardness: 6.5-7 (Mohs scale), Color: Variegated blues, greys, and yellows, Luster: Waxy to vitreous, Crystal structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.6-2.65

Formation & Geological History

Formed through the accumulation of silica-rich organic remains (like radiolarians) or by the chemical precipitation of silica in groundwater or marine environments. This specimen appears water-worn, likely from a fluvial or glacial deposit.

Uses & Applications

Historically used for tool making (flint knapping); currently used for decorative stone, lapidary work, jewelry, and landscaping.

Geological Facts

Chert and its varieties like jasper or flint were among the first resources used by early humans to create sharp tools and weapons due to their predictable conchoidal fracturing.

Field Identification & Locations

Identify by its hardness (will scratch glass), waxy feel, and smooth curved (conchoidal) breaks. Often found in riverbeds or within limestone formations. Collectors look for unique banding or color patterns.

Identified on: 5/1/2026

Mode: Standard