sedimentary
Agate and Jasper
Silicon Dioxide (SiO2) - Microcrystalline Quartz
Hardness of 7 on the Mohs scale. Colors range from brown, orange, yellow to grey and white. Luster is waxy to vitreous. Cryptocrystalline structure with conchoidal fracture. Specific gravity is approximately 2.60 to 2.65.
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Physical properties
Hardness of 7 on the Mohs scale. Colors range from brown, orange, yellow to grey and white. Luster is waxy to vitreous. Cryptocrystalline structure with conchoidal fracture. Specific gravity is approximately 2.60 to 2.65.
Formation & geological history
Formed through the deposition of silica-rich groundwater in cavities of ancient volcanic or sedimentary rocks over millions of years.
Uses & applications
Used in lapidary arts, making jewelry, ornamental carvings, and collected by rockhounds.
Geological facts
Agate is a variety of chalcedony that often forms in concentric bands. Jasper is an opaque, impure variety of quartz that can contain up to 20% foreign materials, which account for its rich colors.
Field identification & locations
Found worldwide in riverbeds, gravel pits, and weathering volcanic regions. Identify by its conchoidal fracture, waxy luster, and resistance to steel scratching.
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