igneous
Brecciated quartz vein rock (likely quartz breccia)
Silicified hydrothermal breccia; predominantly microcrystalline and crystalline SiO₂ (quartz), with possible iron oxides and carbonate minerals
AI-generated identification · may be incorrectHardness about 7 for quartz; gray, white, tan, and brown angular fragments in a lighter silica-rich matrix, with vitreous to dull luster and no obvious cleavage. Specific gravity is typically 2.6–2.7; the angular clasts and crosscutting veins are diagnostic.
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Physical properties
Hardness about 7 for quartz; gray, white, tan, and brown angular fragments in a lighter silica-rich matrix, with vitreous to dull luster and no obvious cleavage. Specific gravity is typically 2.6–2.7; the angular clasts and crosscutting veins are diagnostic.
Formation & geological history
Forms when hydrothermal fluids fracture existing rock and cement the fragments with silica, often with later iron-oxide staining. Such breccias commonly form in volcanic or fault zones from the Cenozoic to older geological ages; the exact age requires locality data.
Uses & applications
Used as decorative facing stone, landscaping rock, and lapidary material when attractive; generally has modest collector value unless strongly patterned, colorful, or associated with ore minerals.
Geological facts
The network of angular clasts distinguishes breccia from conglomerate, whose clasts are rounded. Rusty colors commonly reflect hematite or limonite coating fractures.
Field identification & locations
Identify by its sharp-edged fragments, abundant hard quartz veins, and inability to scratch quartz with a steel knife; it may scratch glass. Common in hydrothermal districts, volcanic terrains, and fault zones worldwide.
