igneous
Weathered quartz-rich rock fragment
Indeterminate; likely altered granite or quartz-bearing pegmatite
AI-generated identification · may be incorrectTan to rusty-brown, coarse granular texture with visible pale quartz/feldspar and darker mica or iron-oxide patches; likely Mohs 6–7, vitreous to dull luster, with no obvious cleavage in quartz but feldspar cleavage. Specific gravity approximately 2.6–2.8.
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Physical properties
Tan to rusty-brown, coarse granular texture with visible pale quartz/feldspar and darker mica or iron-oxide patches; likely Mohs 6–7, vitreous to dull luster, with no obvious cleavage in quartz but feldspar cleavage. Specific gravity approximately 2.6–2.8.
Formation & geological history
Probably a naturally weathered fragment of felsic igneous rock formed from slowly cooling silica-rich magma, commonly Precambrian to Mesozoic depending on locality; the brown coloration reflects surface oxidation and weathering.
Uses & applications
Primarily a field or teaching specimen; unaltered material of this kind is used as aggregate, dimension stone, and occasionally decorative stone, but this fragment has little commercial value.
Geological facts
The image does not show diagnostic crystals or an unweathered surface, so exact identification is uncertain; the adjacent purple stones appear to be polished amethyst, but they are separate specimens.
Field identification & locations
Look for interlocking quartz and feldspar grains, abundant mica, and hardness sufficient to scratch glass; a fresh broken surface and locality information are needed to distinguish granite, pegmatite, and weathered quartzite.
