metamorphic
Dark green-black tumbled stone, possibly nephrite jade
Undetermined; possible nephrite (tremolite–actinolite, Ca₂(Mg,Fe)₅Si₈O₂₂(OH)₂)
AI-generated identification · may be incorrectSmooth, rounded, opaque dark olive-gray surface with a subdued waxy luster. If nephrite, hardness is about 6–6.5 Mohs and its crystals form densely interlocking fibrous aggregates; the photo alone cannot confirm the material.
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Physical properties
Smooth, rounded, opaque dark olive-gray surface with a subdued waxy luster. If nephrite, hardness is about 6–6.5 Mohs and its crystals form densely interlocking fibrous aggregates; the photo alone cannot confirm the material.
Formation & geological history
Nephrite forms through metamorphic alteration, commonly where magnesium-rich rocks interact with fluids; deposits occur in varied geological ages. The specimen appears shaped or tumbled, obscuring natural surfaces.
Uses & applications
Nephrite is carved for jewelry and ornaments; similar-looking dark stones may be sold as decorative tumbled material.
Geological facts
Nephrite is notably tough because of its interwoven amphibole fibers; appearance alone is not a reliable jade identification.
Field identification & locations
The image shows a small polished pebble, but color and shape are insufficient to distinguish jade from other dark stones. Common nephrite sources include China, British Columbia, New Zealand, and Siberia; confirm with gemological tests before identifying or valuing it.
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