igneous
Weathered granite or granitic gneiss
Granite; primarily quartz, feldspar, and mica (possibly metamorphosed to gneiss)
AI-generated identification · may be incorrectMedium- to coarse-grained, gray and mottled white with rusty iron-oxide staining; granular texture, vitreous quartz, no obvious cleavage in the whole rock. Typical hardness is about 6–7 Mohs and specific gravity 2.6–2.8.
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Physical properties
Medium- to coarse-grained, gray and mottled white with rusty iron-oxide staining; granular texture, vitreous quartz, no obvious cleavage in the whole rock. Typical hardness is about 6–7 Mohs and specific gravity 2.6–2.8.
Formation & geological history
Formed by slow crystallization of silica-rich magma deep underground, commonly during Precambrian to Phanerozoic mountain-building; strong banding, if present, would indicate later metamorphism into gneiss.
Uses & applications
Used as crushed aggregate, building stone, countertops, monuments, and landscaping material; attractive polished pieces may be collected but are usually low value.
Geological facts
The orange-brown areas are likely limonite or hematite produced by weathering of iron-bearing minerals such as biotite. The photograph does not clearly resolve mineral grains or foliation, so exact identification requires a fresh surface.
Field identification & locations
Common worldwide, especially in continental shields and mountain belts. Look for interlocking quartz and feldspar grains, scattered dark mica, and resistance to scratching by a steel knife; value is generally $1–$20 for an ordinary specimen, or $20–$100+ if unusually patterned or polished.
