Chalcedony
Variety of quartz
Common · SiO₂
A cryptocrystalline variety of silica with fibrous internal structure invisible to the naked eye. Encompasses agate, jasper, onyx, and chrysoprase. Forms in vesicles of volcanic rocks and in low-temperature hydrothermal environments.
Identity
- Formula
- SiO₂
- Chemical class
- Silicate
- Varieties
- Agate, Bloodstone, Carnelian, Moss Agate
- Mineral group
- Amethyst, Citrine, Jasper, Onyx, Quartz, Rose Quartz, Smoky Quartz, Tiger's Eye
- Also known as
- Agate (banded), Jasper (opaque), Onyx (layered black-white), Chrysoprase (green)
- Used in alchemy
- Chalcedony Powder
Crystallography
- Crystal system
- Trigonal
- Habits
- Massive, Botryoidal, Stalactitic, Nodular
- Fracture
- Conchoidal
Physical properties
- Mohs hardness
- 6.5
- Density
- 2.6 g/cm³
- Luster
- Waxy, Dull
- Colors
- white, gray, blue, red, brown, green, yellow, multicolored
- Streak
- white
- Transparency
- Translucent, Opaque
Geology
- Origins
- Hydrothermal, Sedimentary, Volcanic
- Host rocks
- Volcanic rock, Limestone and chalk
- Associated minerals
- Quartz, Opal, Calcite
- Found in
- Jasper
- Geography
- worldwide
Classification
- Rarity
- Common
- Gem quality
- Yes
Sources
- Chalcedony. Mindat.org (Hudson Institute of Mineralogy).
- Chalcedony. Gemdat.org (Hudson Institute of Mineralogy).
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