mineral
Chalcedony / Agate Pebble
Silicon Dioxide (SiO2)
AI-generated identification · may be incorrectHardness: 6.5-7 on Mohs scale; Color: Purple, lavender, white, gray; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline/cryptocrystalline); Cleavage: None, conchoidal fracture
- Hardness
- 6
- Color
- Purple, lavender, white, gray
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 on Mohs scale; Color: Purple, lavender, white, gray; Luster: Waxy to vitreous; Crystal structure: Trigonal (microcrystalline/cryptocrystalline); Cleavage: None, conchoidal fracture
Formation & geological history
Formed via precipitation of silica-rich solutions within cavity vesicles of volcanic rocks or sedimentary environments over millions of years, later weathered out and rounded by water transport.
Uses & applications
Lapidary work, tumbling, jewelry beads, cabochons, and rock collecting.
Geological facts
Agate and chalcedony are cryptocrystalline varieties of quartz. Purple shades often come from trace iron or manganese impurities within the silica matrix.
Field identification & locations
Look for waxy luster, smooth water-worn surface with subtle translucency, and conchoidal fractures. Commonly found on riverbanks, beaches, and gravel beds.
