mineral
Tumbled dark stone, possibly hematite or black jasper
Uncertain; likely hematite (Fe₂O₃) or fine-grained chalcedony/jasper (SiO₂)
AI-generated identification · may be incorrectSmooth, rounded, opaque dark gray-black with a glossy polish; likely Mohs hardness 5.5–6.5 (hematite ~5–6.5; jasper ~6.5–7). Crystal structure is not visible because it is tumbled and fine-grained; hematite has a metallic-to-earthy luster, while jasper is vitreous.
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Physical properties
Smooth, rounded, opaque dark gray-black with a glossy polish; likely Mohs hardness 5.5–6.5 (hematite ~5–6.5; jasper ~6.5–7). Crystal structure is not visible because it is tumbled and fine-grained; hematite has a metallic-to-earthy luster, while jasper is vitreous.
Formation & geological history
A human-tumbled specimen, but the source material likely formed through iron-oxide mineralization or silica-rich volcanic/sedimentary processes, generally over millions of years. The image is insufficient for definitive identification.
Uses & applications
Commonly used in lapidary work, worry stones, crafts, and inexpensive jewelry; hematite is also an iron ore, while jasper is ornamental rather than economically mined for metal.
Geological facts
Hematite is unusually heavy and may leave a reddish-brown streak on unglazed ceramic; jasper generally does not. A magnet test is unreliable because some hematite is weakly magnetic and some specimens contain magnetite.
Field identification & locations
Check streak, weight, hardness, and polish: a red-brown streak suggests hematite; glass-scratching hardness and conchoidal chips favor jasper/chalcedony. Common sources include Brazil, India, Mexico, South Africa, and the United States.
