metamorphic
Hydrothermal Quartz Breccia
Hydrothermal Breccia with Quartz and Chloritic/Epidote Clasts
Hardness: 6.5-7 (quartz matrix); Color: White matrix with green and grey clasts; Luster: Vitreous to dull; Structure: Fragmental/Brecciated; Cleavage: None (conchoidal fracture)
- Hardness
- 6
- Color
- White matrix with green and grey clasts
- Luster
- Vitreous to dull
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Physical properties
Hardness: 6.5-7 (quartz matrix); Color: White matrix with green and grey clasts; Luster: Vitreous to dull; Structure: Fragmental/Brecciated; Cleavage: None (conchoidal fracture)
Formation & geological history
Formed via hydrothermal fracturing where high-pressure fluids (typically in volcanic or tectonic settings) shatter existing rock, followed by the precipitation of quartz from those fluids to cement the fragments together.
Uses & applications
Primarily of interest to geologists and collectors. Sometimes used as decorative stone or landscaping rock. In mining, these formations are often indicators of nearby mineral deposits like gold or copper.
Geological facts
The angularity of the fragments indicates they were cemented almost immediately after being broken, as they show very little rounding from transport. The green color in the fragments suggests the presence of chlorite or epidote minerals.
Field identification & locations
Identify by the sharp, angular fragments of older rock trapped within a different-colored mineral vein (the matrix). Common in mountain belts, fault zones, and areas with past volcanic activity.
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