igneous
Brecciated quartz-rich rock (probable vein breccia)
Hydrothermal quartz breccia; predominantly SiO₂ quartz clasts in iron-oxide-rich cement
AI-generated identification · may be incorrectWhite to gray angular quartz fragments in brown limonite/goethite matrix; vitreous luster, granular texture, irregular fracture, no obvious cleavage; quartz hardness ~7 Mohs and specific gravity ~2.65. The rounded shape appears water-worn, but the original texture is angular breccia.
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Physical properties
White to gray angular quartz fragments in brown limonite/goethite matrix; vitreous luster, granular texture, irregular fracture, no obvious cleavage; quartz hardness ~7 Mohs and specific gravity ~2.65. The rounded shape appears water-worn, but the original texture is angular breccia.
Formation & geological history
Forms when hydrothermal fluids fracture preexisting rock and precipitate quartz and iron oxides in the openings, commonly during episodic faulting. The exact geological age cannot be determined from the image and depends on its host deposit.
Uses & applications
Used mainly as a collector specimen, lapidary material, or decorative stone; iron-rich varieties may be associated with gold or other hydrothermal mineralization, but this specimen is not proof of ore value.
Geological facts
Angular clasts cemented by a contrasting matrix distinguish breccia from conglomerate, whose clasts are rounded. Brown coloration is commonly produced by weathering of iron-bearing minerals.
Field identification & locations
Look for sharp-edged quartz fragments, sugary/vitreous surfaces, and quartz’s ability to scratch glass; dilute acid should not visibly fizz. Common in fault zones and epithermal mineral districts worldwide.
