igneous
Weathered granitic or feldspathic pebble
Likely granite/granodiorite; quartz–feldspar–mica aggregate
AI-generated identification · may be incorrectCoarse-grained, speckled tan-gray matrix with visible pale crystals and darker minerals; vitreous to dull luster, no obvious cleavage as a whole, Mohs hardness about 6–7, and typical specific gravity 2.6–2.8.
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Physical properties
Coarse-grained, speckled tan-gray matrix with visible pale crystals and darker minerals; vitreous to dull luster, no obvious cleavage as a whole, Mohs hardness about 6–7, and typical specific gravity 2.6–2.8.
Formation & geological history
Formed when silica-rich magma slowly cooled and crystallized deep underground, commonly during Precambrian to Phanerozoic continental crust formation; later erosion produced the rounded pebble.
Uses & applications
Used as aggregate, landscaping stone, paving material, and dimension stone; this small weathered specimen has little commercial value but can be useful for teaching mineral identification.
Geological facts
The granular texture indicates interlocking crystals rather than a glassy or sedimentary matrix. The brown coating is likely iron-oxide weathering (limonite) or surface staining.
Field identification & locations
Identify it by its visible interlocking quartz/feldspar grains, hardness, and lack of layering or foliation; common in stream gravels and glacial deposits worldwide. A streak test, hand lens, and acid test can help distinguish it from sandstone or altered volcanic rock.
