mineral
Chalcedony with iron-oxide staining
Microcrystalline quartz (SiO₂), likely chalcedony or chert with limonite/goethite staining
AI-generated identification · may be incorrectHardness about 6.5–7 Mohs; pale gray-beige, waxy to dull luster, opaque to slightly translucent, with a rusty orange-brown iron-oxide patch. Quartz has no cleavage, conchoidal fracture, and specific gravity near 2.6.
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Physical properties
Hardness about 6.5–7 Mohs; pale gray-beige, waxy to dull luster, opaque to slightly translucent, with a rusty orange-brown iron-oxide patch. Quartz has no cleavage, conchoidal fracture, and specific gravity near 2.6.
Formation & geological history
Silica-rich groundwater deposited microcrystalline quartz in cavities or fractures, later acquiring iron-oxide staining from weathering. The specimen’s exact geological age cannot be determined from the image.
Uses & applications
Used for ornamental stone, carvings, cabochons, abrasives, and lapidary study; this small rough piece has limited commercial value.
Geological facts
Chalcedony is quartz made of extremely small intergrown crystals, often producing a smooth waxy appearance. Orange-brown coloration commonly comes from limonite or goethite rather than the quartz itself.
Field identification & locations
Test for glass-scratching hardness and inspect for conchoidal fracture; an opaque, granular interior may indicate chert. Common in volcanic cavities, sedimentary nodules, and weathered silica-rich rocks worldwide.
