igneous
Weathered granite or granitic gneiss
Granite; primarily quartz, feldspar, and mica (exact identification uncertain from the photo)
AI-generated identification · may be incorrectCoarse, irregular gray-tan specimen with a dull earthy luster and apparent interlocking grains; likely Mohs hardness about 6–7, with no obvious cleavage as a whole rock. The low light and small size obscure mineral details.
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Physical properties
Coarse, irregular gray-tan specimen with a dull earthy luster and apparent interlocking grains; likely Mohs hardness about 6–7, with no obvious cleavage as a whole rock. The low light and small size obscure mineral details.
Formation & geological history
Granite crystallizes slowly from silica-rich magma deep underground; gneiss is its metamorphic equivalent. Precambrian granitic rocks are widespread around northeastern Minnesota and commonly occur as glacially transported cobbles.
Uses & applications
Used as crushed stone, building and monument stone, countertops, and aggregate; small pieces have modest collecting value.
Geological facts
The reported location near 46.7°N, 92.0°W lies in the Precambrian Canadian Shield/Lake Superior region, where granite, gneiss, basalt, and iron-rich metamorphic rocks are common.
Field identification & locations
Look for visible quartz, pink or white feldspar, and black mica in a granular texture; a streak test is usually white, and glass can be scratched by individual quartz grains. A fresh surface or brighter lighting would improve identification.
