metamorphic
Quartz-veined metamorphic rock, likely greenschist or altered metavolcanic
Chlorite–actinolite–epidote-bearing metavolcanic rock with quartz veins; exact identification requires testing
AI-generated identification · may be incorrectFine- to medium-grained, green-gray matrix with dark blue-black mineral patches and a prominent white quartz vein. Quartz is Mohs 7 with glassy luster; the darker minerals are likely amphibole, chlorite, or epidote. No obvious crystal faces or cleavage are visible.
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Physical properties
Fine- to medium-grained, green-gray matrix with dark blue-black mineral patches and a prominent white quartz vein. Quartz is Mohs 7 with glassy luster; the darker minerals are likely amphibole, chlorite, or epidote. No obvious crystal faces or cleavage are visible.
Formation & geological history
Probably metamorphosed volcanic rock or hydrothermally altered mafic rock, later fractured and filled by silica-rich fluids. Such rocks commonly formed during regional metamorphism in ancient accreted volcanic belts; age cannot be determined from the photograph.
Uses & applications
Primarily a geological/collector specimen; occasionally used as decorative stone if larger and attractive. It is not identifiable as a gemstone from the image alone.
Geological facts
The white band is most consistent with quartz, while the dark patches may be hornblende, actinolite, chlorite, or magnetite. A strong response to a magnet would support magnetite-bearing altered basalt.
Field identification & locations
The specimen is visually consistent with rocks from volcanic and metamorphic belts near Sinaloa, Mexico, but locality alone is insufficient. Test streak, hardness, magnetism, and acid reaction; quartz should scratch glass, while the matrix may not.
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