mineral
Polished Tumbled Stone (Dark Chalcedony / Jasper)
Silicon Dioxide (SiO2)
Hardness: 6.5 - 7 on the Mohs scale. Color: Dark gray, blackish, with slight reddish or brown speckling. Luster: Vitreous to waxy after polishing. Crystal System: Trigonal (microcrystalline/cryptocrystalline). Cleavage: None, exhibits conchoidal fracture.
- Hardness
- 6
- Color
- Dark gray, blackish, with slight reddish or brown speckling
- Luster
- Vitreous to waxy after polishing
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Physical properties
Hardness: 6.5 - 7 on the Mohs scale. Color: Dark gray, blackish, with slight reddish or brown speckling. Luster: Vitreous to waxy after polishing. Crystal System: Trigonal (microcrystalline/cryptocrystalline). Cleavage: None, exhibits conchoidal fracture.
Formation & geological history
Formed through the precipitation of silica-rich solutions in cavities of volcanic or sedimentary rocks, followed by tumbling and polishing.
Uses & applications
Used primarily as decorative tumbled stones, pocket stones, wire-wrapped jewelry, and in rock collections.
Geological facts
Tumbled stones are machine-polished using abrasive grits over several weeks to smooth out rough natural edges and produce a glossy finish.
Field identification & locations
Identified by its smooth, polished texture, high hardness (scratches glass), lack of visible cleavage, and dark mottled coloration. Common worldwide.
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