igneous
Weathered copper-bearing porphyritic rock (probable andesite or altered volcanic rock)
Likely propylitically altered andesite/latite; green color may reflect chlorite, epidote, or chrysocolla/malachite staining
AI-generated identification · may be incorrectGray-green, dull to weakly sparkling, fine-grained and possibly porphyritic, with a rusty-brown weathered surface. Hardness likely about 5–7 overall; cleavage absent or poor; specific gravity approximately 2.6–2.9.…
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Physical properties
Gray-green, dull to weakly sparkling, fine-grained and possibly porphyritic, with a rusty-brown weathered surface. Hardness likely about 5–7 overall; cleavage absent or poor; specific gravity approximately 2.6–2.9. The image does not show diagnostic crystal faces or enough detail for a definitive mineral identification.
Formation & geological history
Probably volcanic rock altered by hydrothermal fluids, with oxidation producing brown iron staining; copper minerals may account for the green surface. Such rocks commonly formed in Tertiary volcanic terrains, including the Globe-Miami region of Arizona, rather than having a single identifiable age from appearance alone.
Uses & applications
Usually a common field specimen or ore-host rock, with little value unless assays show significant copper, gold, or silver. Cut pieces may be attractive but are not typically jewelry grade.
Geological facts
The reported location is strongly compatible with altered copper-mineralized volcanic rocks and porphyry-copper districts. A visible green color alone does not prove malachite or chrysocolla; testing is needed.
Field identification & locations
Look for copper carbonates, veinlets, and blue-green coatings; a streak, hardness test, dilute acid test, and specific-gravity measurement would help. A copper assay is the most useful test; avoid relying on color alone.
