metamorphic
Polished quartz-rich breccia
Quartz–feldspar breccia; predominantly SiO₂ with feldspar and iron-oxide minerals
AI-generated identification · may be incorrectHardness about 6–7 Mohs; cream, tan, brown, and gray coloration with vitreous to dull luster. Angular pale fragments are cemented by darker quartz/iron-oxide material; massive, non-cleavable overall, with specific gravity roughly 2.6–2.7.
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Physical properties
Hardness about 6–7 Mohs; cream, tan, brown, and gray coloration with vitreous to dull luster. Angular pale fragments are cemented by darker quartz/iron-oxide material; massive, non-cleavable overall, with specific gravity roughly 2.6–2.7.
Formation & geological history
Formed when fractured quartz- and feldspar-rich rock was cemented by silica and later altered by iron-bearing fluids, likely during hydrothermal or tectonic activity. Its exact geological age cannot be determined from the photograph.
Uses & applications
Used mainly as a polished ornamental stone, cabochon, or lapidary specimen; occasionally used for decorative tile or aggregate. It has modest jewelry and collecting value.
Geological facts
The contrasting angular clasts and dark cement distinguish breccia from banded agate or ordinary granite. Brown coloration commonly results from hematite or limonite staining.
Field identification & locations
Look for hard, glassy quartz grains, angular clasts, irregular veins, and resistance to scratching by a steel blade. Common varieties occur in hydrothermal veins, fault zones, and silicified breccia deposits worldwide.
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