mineral
Quartz (Chalcedony/Agate)
Silicon Dioxide (SiO2)
Hardness: 7 on Mohs scale; Color: translucent white to pale yellow/grey; Luster: waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: none (conchoidal fracture); Specific Gravity: 2.65
- Hardness
- 7 on Mohs scale
- Color
- translucent white to pale yellow/grey
- Luster
- waxy to vitreous
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Physical properties
Hardness: 7 on Mohs scale; Color: translucent white to pale yellow/grey; Luster: waxy to vitreous; Crystal Structure: Trigonal (microcrystalline); Cleavage: none (conchoidal fracture); Specific Gravity: 2.65
Formation & geological history
Formed by the deposition of silica from groundwater in cavities of igneous and sedimentary rocks over millions of years.
Uses & applications
Used for lapidary work, jewelry (beads and cabochons), and as a collector's specimen.
Geological facts
This specimen appears to be a water-worn or tumbled piece of chalcedony, a cryptocrystalline variety of quartz. It is one of the most common minerals in the Earth's crust.
Field identification & locations
Identify by its hardness (will scratch glass), waxy luster when tumbled, and lack of visible crystal faces. Commonly found in riverbeds and gravel pits.
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