mineral
Polished plume agate
Microcrystalline quartz (SiO₂), variety of chalcedony
AI-generated identification · may be incorrectMohs hardness 6.5–7; glossy vitreous-to-waxy luster, translucent gray, cream, and brown areas with dark plume-like inclusions. Trigonal quartz at the microscopic level; no cleavage and conchoidal fracture.
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Physical properties
Mohs hardness 6.5–7; glossy vitreous-to-waxy luster, translucent gray, cream, and brown areas with dark plume-like inclusions. Trigonal quartz at the microscopic level; no cleavage and conchoidal fracture.
Formation & geological history
Silica-rich fluids deposited chalcedony in cavities or fractures, with iron and other mineral inclusions creating the plumes. The exact locality and geological age cannot be determined from the photo.
Uses & applications
Polished agate is used for jewelry, ornaments, and lapidary collecting; agate is also used for small precision components.
Geological facts
The specimen appears tumbled or otherwise polished; its dark, branching internal patterns are characteristic of plume-style agate.
Field identification & locations
Look for waxy translucence, curved banding or plume inclusions, and conchoidal fracture; common sources include Brazil, Uruguay, India, and the western United States. A simple scratch test can help distinguish it from softer imitations, but avoid damaging a polished piece.
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