igneous
Quartz-rich feldspathic rock, likely granite or granitic pegmatite
Granite/pegmatite composed mainly of quartz (SiO₂) and feldspar, with minor mica or iron-oxide staining
AI-generated identification · may be incorrectCoarse, irregular granular texture; white to cream with brown staining; vitreous to dull luster. Quartz hardness is 7 and feldspar about 6–6.5; no obvious cleavage is visible at this resolution, though feldspar commonly has two cleavage planes. Typical specific gravity is about 2.6–2.7.
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Physical properties
Coarse, irregular granular texture; white to cream with brown staining; vitreous to dull luster. Quartz hardness is 7 and feldspar about 6–6.5; no obvious cleavage is visible at this resolution, though feldspar commonly has two cleavage planes. Typical specific gravity is about 2.6–2.7.
Formation & geological history
Forms when silica-rich magma slowly cools and crystallizes underground; pegmatitic varieties develop from late, water-rich magma and may contain unusually large crystals. Such rocks range from Precambrian to recent intrusive bodies.
Uses & applications
Used as building stone, aggregate, countertops, monuments, and landscaping material; attractive quartz-rich pieces may be collected but are usually low-value.
Geological facts
Brown coloration commonly comes from weathering or iron-oxide coatings on feldspar and fractures. Visible interlocking quartz and feldspar grains distinguish it from limestone or manufactured stone.
Field identification & locations
Common in continental mountain belts and exposed intrusive terrains worldwide, including New England, the Appalachians, Scandinavia, and India. A glassy, translucent grain suggests quartz; blocky grains with cleavage suggest feldspar.
