mineral
Chalcedony Pebble / Rough Agate
Silicon Dioxide (SiO2)
Hardness: 6.5 - 7 on Mohs scale. Color: Brownish-orange, tan, translucence along thin edges. Luster: Waxy to resinous. Fracture: Conchoidal. Crystal system: Microcrystalline trigonal.
- Hardness
- 6
- Color
- Brownish-orange, tan, translucence along thin edges
- Luster
- Waxy to resinous
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Physical properties
Hardness: 6.5 - 7 on Mohs scale. Color: Brownish-orange, tan, translucence along thin edges. Luster: Waxy to resinous. Fracture: Conchoidal. Crystal system: Microcrystalline trigonal.
Formation & geological history
Formed by low-temperature deposition of silica from water solutions in cavity openings, gas bubbles, or fractures within volcanic, metamorphic, or sedimentary rocks. Over time, weathering releases these hard nodules into stream beds and soil horizons.
Uses & applications
Used in lapidary work, cabochon cutting, jewelry, and as raw material for tumbled gemstones or decorative polished stones.
Geological facts
Chalcedony is a cryptocrystalline variety of quartz, composed of very fine intergrowths of quartz and moganite. Translucent, weathered specimens like this often reveal colorful banding or clarity when sliced and polished.
Field identification & locations
Identified by its smooth, water-worn exterior, waxy luster, conchoidal fracture, and translucency when held up to a light source. Commonly found in gravel beds, desert pavements, and alluvial deposits globally.
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