sedimentary
Agate
Silicon Dioxide (Chalcedony), SiO2
Hardness of 6.5 to 7 on the Mohs scale, colors vary widely including brown, black, grey, white, and translucent patches, waxy to vitreous luster, microcrystalline (cryptocrystalline) quartz structure, no true cleavage, specific gravity of 2.58 to 2.64.
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Physical properties
Hardness of 6.5 to 7 on the Mohs scale, colors vary widely including brown, black, grey, white, and translucent patches, waxy to vitreous luster, microcrystalline (cryptocrystalline) quartz structure, no true cleavage, specific gravity of 2.58 to 2.64.
Formation & geological history
Formed primarily within cavities of volcanic and metamorphic rocks through the deposition of silica-rich groundwater solutions in concentric layers over millions of years.
Uses & applications
Used in jewelry, decorative ornaments, gemstone carvings, and industrial applications such as mortar and pestle sets due to its hardness.
Geological facts
Agate is often found in ancient lava flows where silica-bearing solutions filled gas bubbles, creating distinct banded patterns when sliced and polished.
Field identification & locations
Can be identified in the field by its waxy luster, conchoidal fracture, and often rounded, water-worn pebble shape with translucent or banded layers visible when wet.
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