sedimentary
Banded Agate
Chalcedony (Silicon Dioxide, SiO2)
Hardness: 6.5-7 Mohs; Color: Brown, tan, and white banding; Luster: Waxy to vitreous; Structure: Microcrystalline; Cleavage: None (conchoidal fracture).
- Hardness
- 6
- Color
- Brown, tan, and white banding
- Luster
- Waxy to vitreous
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Physical properties
Hardness: 6.5-7 Mohs; Color: Brown, tan, and white banding; Luster: Waxy to vitreous; Structure: Microcrystalline; Cleavage: None (conchoidal fracture).
Formation & geological history
Forms through the deposition of silica from groundwater in the cavities of igneous rocks or sedimentary formations, often in layers over thousands of years.
Uses & applications
Used primarily in jewelry, lapidary arts, decorative carvings, and as a collector's specimen.
Geological facts
Agate is a variety of chalcedony characterized by its fineness of grain and brightness of color. It was named by Theophrastus, a Greek philosopher, who found the stone along the Achates River.
Field identification & locations
Identify by looking for concentric or parallel banding and a waxy surface. Often found in riverbeds, volcanic fields, and gravel deposits.
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