Agate
Variety of chalcedony
Common · SiO₂
A banded, fibrous chalcedony that lines cavities in volcanic rocks, grown at between about 20 and 200 °C. The bands record the filling of the cavity layer by layer, and the horizontal ones still show which way was down when the stone formed. Named for the Achates river in Sicily.
Identity
- Formula
- SiO₂
- Chemical class
- Silicate
- Varieties
- Onyx
- Mineral group
- Amethyst, Bloodstone, Carnelian, Chalcedony, Citrine, Jasper, Moss Agate, Quartz, Rose Quartz, Smoky Quartz, Tiger's Eye
- Also known as
- Achates, Banded chalcedony
Crystallography
- Crystal system
- Trigonal
- Habits
- Nodular, Massive
- Fracture
- Conchoidal
Physical properties
- Mohs hardness
- 6.5
- Density
- 2.6 g/cm³
- Luster
- Waxy, Dull
- Colors
- colorless, gray, red, white, violet, multicolored
- Streak
- white
- Transparency
- Translucent
Geology
- Origins
- Volcanic, Hydrothermal, Sedimentary
- Host rocks
- Volcanic rock
- Associated minerals
- Chalcedony, Quartz
- Geography
- USA, Germany, Brazil, Mexico (Chihuahua), Botswana, Italy (Sicily)
Classification
- Rarity
- Common
- Gem quality
- Yes
Arcane properties
- Affinity
- Earth
- Effects
- Warding
- Planar origin
- Material Plane
Sources
- Agate. Mindat.org (Hudson Institute of Mineralogy).
- Chalcedony. Mindat.org (Hudson Institute of Mineralogy).
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