igneous
Drill core of probable granite or granodiorite
Crystalline quartz–feldspar–mica rock; exact composition cannot be confirmed from the photograph
AI-generated identification · may be incorrectLight gray, massive, fine- to medium-grained, with weakly visible interlocking crystals and weathered surfaces; likely Mohs 6–7, vitreous to dull luster, negligible cleavage as a rock, and specific gravity about 2.6–2.8.
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Physical properties
Light gray, massive, fine- to medium-grained, with weakly visible interlocking crystals and weathered surfaces; likely Mohs 6–7, vitreous to dull luster, negligible cleavage as a rock, and specific gravity about 2.6–2.8.
Formation & geological history
Likely slowly cooled intrusive magma, forming crystalline plutonic rock millions to billions of years ago; the cylindrical shape is human-drilled core, not natural morphology.
Uses & applications
Used as geological exploration core for mapping bedrock, mineral resources, engineering conditions, and groundwater. Unlikely to have jewelry value unless it contains unusual minerals or ore.
Geological facts
The specimen appears to be an oriented exploration core, with a dark fracture or vein crossing it. Granite and granodiorite commonly contain quartz, potassium feldspar, plagioclase, and biotite or hornblende.
Field identification & locations
Identify it in the field by its hard, speckled crystalline texture, lack of bedding or vesicles, and inability to scratch easily with a steel knife. A thin section or chemical analysis is needed to distinguish granite, granodiorite, tonalite, or altered rock.
