igneous
Quartz-rich granitic rock, possibly pegmatite
Granite or granitic pegmatite; primarily quartz (SiO₂), feldspar, and minor mica/iron oxides
AI-generated identification · may be incorrectA pale, coarse-grained specimen with translucent white-gray material and brown mineral staining. Quartz has Mohs hardness 7 and vitreous luster; feldspar is about 6–6.5, with no obvious cleavage visible at this image quality.
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Physical properties
A pale, coarse-grained specimen with translucent white-gray material and brown mineral staining. Quartz has Mohs hardness 7 and vitreous luster; feldspar is about 6–6.5, with no obvious cleavage visible at this image quality.
Formation & geological history
Formed when silica-rich magma cooled slowly underground, allowing interlocking crystals to grow; broadly Precambrian to Phanerozoic depending on its source. Brown areas may be weathered biotite or iron-oxide alteration.
Uses & applications
Used as crushed stone, building stone, countertops, and aggregate; attractive pieces may be collected, though this specimen appears common and not gem quality.
Geological facts
Pegmatites are exceptionally coarse-grained and can host large quartz, feldspar, mica, and rare-element crystals. A closer, well-lit view would be needed to distinguish ordinary granite from pegmatite or quartz vein material.
Field identification & locations
Common in continental crust, especially around granite intrusions worldwide. Look for visible interlocking quartz and feldspar grains, hardness greater than glass, and lack of fizz with dilute acid.
