Sedimentary/Metamorphic

Brecciated Jasper or Chert

SiO2

Hardness: 6.5-7 on Mohs scale. Color: Gray, black, and white with a webbed or fractured appearance. Luster: Dull to waxy. Crystal structure: Cryptocrystalline. Cleavage: None, exhibits conchoidal fracture. Specific gravity: ~2.6.

Hardness: 6
Color: Gray, black, and white with a webbed or fractured appearance
Luster: Dull to waxy

Identified May 31, 2026More sedimentary/metamorphic →

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Physical properties

Formation & geological history

Formed from silica-rich fluids that percolated through fractured rock, typically in sedimentary or low-grade metamorphic environments. The 'brecciated' texture is a result of the original rock being broken into fragments and then cemented together by a fine-grained silica matrix.

Uses & applications

Primarily collected for lapidary uses, such as tumbling, cabochons, and ornamental pieces.

Geological facts

The distinctive 'spider web' pattern is a classic feature of brecciated stones, where the dark veins represent the matrix filling the fractures of the original rock.

Field identification & locations

Can be identified by its distinctive fractured and re-cemented appearance, hardness (can scratch glass), and waxy luster. Commonly found in areas with a history of tectonic activity and silica-rich hydrothermal fluids.