metamorphic
Tumbled yellow-green pebble, likely serpentine or quartzite
Provisional: serpentine-group rock, chiefly Mg₃Si₂O₅(OH)₄; exact identification requires testing
AI-generated identification · may be incorrectSmooth, rounded, opaque, yellow-green specimen with mottled orange staining and a dull-to-waxy luster. Likely Mohs 3–7 depending on composition; no visible cleavage or crystal faces, and the image does not permit reliable density or structure measurement.
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Physical properties
Smooth, rounded, opaque, yellow-green specimen with mottled orange staining and a dull-to-waxy luster. Likely Mohs 3–7 depending on composition; no visible cleavage or crystal faces, and the image does not permit reliable density or structure measurement.
Formation & geological history
If serpentine, it formed when ultramafic mantle rock was hydrated during metamorphism, commonly in oceanic crust and subduction zones. If quartzite, it is metamorphosed sandstone; geological age depends on its source locality.
Uses & applications
Suitable as a decorative tumbled stone, paperweight, or teaching specimen; serpentine may be carved, while quartzite is used as aggregate and building stone. This isolated pebble has little commercial value.
Geological facts
Yellow-green coloration can result from serpentine minerals, iron oxides, or weathering. A hardness test, streak, and specific-gravity measurement are needed to distinguish serpentine from quartzite, jasper, or other altered rocks.
Field identification & locations
Commonly found in stream gravels and near serpentinized ultramafic rocks; serpentine is widespread in California, Italy, New Zealand, and parts of Canada. Scratch testing with steel and glass, plus a close look for fibrous or waxy texture, is useful.
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