Onyx
Variety of agate
Uncommon · SiO₂
An agate with straight parallel bands, traditionally black and white (brown and white is sardonyx). Much commercial onyx is agate darkened by soaking in sugar and then acid. The "Mexican onyx" of carvings, chess sets and cheap jewellery is not onyx at all but banded calcite from caves (cave onyx), a much softer stone (hardness 3).
Identity
- Formula
- SiO₂
- Chemical class
- Silicate
- Mineral group
- Agate, Amethyst, Bloodstone, Carnelian, Chalcedony, Citrine, Jasper, Moss Agate, Quartz, Rose Quartz, Smoky Quartz, Tiger's Eye
- Also known as
- Sardonyx (brown and white)
- Used in alchemy
- Onyx Powder
Crystallography
- Crystal system
- Trigonal
- Habits
- Nodular, Massive
- Fracture
- Conchoidal
Physical properties
- Mohs hardness
- 6.5
- Density
- 2.6 g/cm³
- Luster
- Waxy
- Colors
- black, white, brown
- Streak
- white
- Transparency
- Translucent, Opaque
Geology
- Origins
- Volcanic, Hydrothermal
- Host rocks
- Volcanic rock
- Associated minerals
- Agate, Chalcedony, Quartz
- Geography
- USA, Argentina, Germany, Brazil, India
Classification
- Rarity
- Uncommon
- Gem quality
- Yes
Arcane properties
- Affinity
- Shadow, Earth
- Effects
- Warding
- Planar origin
- Material Plane
Sources
- Onyx. Mindat.org (Hudson Institute of Mineralogy).
- Cave Onyx. Mindat.org (Hudson Institute of Mineralogy).
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