sedimentary

Chert (Green and Black Jasper variant)

Cryptocrystalline Quartz (SiO2)

AI-generated identification · may be incorrect

Hardness: 6.5-7 (Mohs scale), Color: Olive green and dark charcoal black, Luster: Waxy to vitreous, Crystal Structure: Trigonal (microcrystalline), Cleavage: None (conchoidal fracture), Specific Gravity: 2.5-2.8.

Hardness: 6

Identified June 28, 2026More sedimentary →

Explore Chert (Green and Black Jasper variant) 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 via the accumulation of silica-rich organic remains (like radiolaria or diatoms) or chemical precipitation from hydrothermal fluids. The different colors suggest varying mineral inclusions like chlorite for green and organic matter or manganese for black.

Uses & applications

Historically used for stone tools and weapons due to its sharp conchoidal fracture. Currently used for lapidary work, jewelry (as river-polished stones), and as decorative landscaping gravel.

Geological facts

This specimen is a water-worn river pebble. The distinct color zoning is common in 'polychrome' jaspers where different chemical environments affected the rock during its formation or mineralization.

Field identification & locations

Identify by its smooth texture, extreme hardness (will scratch glass), and waxy appearance. Often found in riverbeds, glacial tills, or coastal beaches where wave action polishes the stone naturally.