Mineral / Sedimentary
Agate
SiO2 (Silicon Dioxide - Chalcedony)
Hardness: 6.5-7 on the Mohs scale. Color: Highly variable, this specimen is translucent with gray/blue banding. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline (microcrystalline quartz).
- Hardness
- 6
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 on the Mohs scale. Color: Highly variable, this specimen is translucent with gray/blue banding. Luster: Waxy to vitreous. Crystal structure: Cryptocrystalline (microcrystalline quartz).
Formation & geological history
Forms primarily in cavities of eruptive rocks or ancient lavas. Silica-rich water percolates through the rock, depositing layers of silica gel concentrically on the walls of the cavity.
Uses & applications
Used in jewelry, decorative items, healing stones, and previously for precision instruments due to its hardness.
Geological facts
Agate was named by the Greek philosopher Theophrastus, who discovered the stone along the shoreline of the river Achates (now the Dirillo River) in Sicily.
Field identification & locations
Identified by its distinctive banding and translucency. Common locations include Brazil, Uruguay, Mexico, and the USA (e.g., Lake Superior region).
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