sedimentary
Green Onyx (Banded Calcite)
Travertine (CaCO3 - Calcium Carbonate)
Hardness: 3 on Mohs scale; Color: Ranges from light green to deep olive with white or cream banding; Luster: Vitreous to waxy; Crystal Structure: Trigonal/Hexagonal (microcrystalline); Cleavage: Perfect rhombohedral (though often hidden in massive form); Specific Gravity: 2.71
- Hardness
- 3 on Mohs scale
- Luster
- Vitreous to waxy
Identified More sedimentary →
Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 3 on Mohs scale; Color: Ranges from light green to deep olive with white or cream banding; Luster: Vitreous to waxy; Crystal Structure: Trigonal/Hexagonal (microcrystalline); Cleavage: Perfect rhombohedral (though often hidden in massive form); Specific Gravity: 2.71
Formation & geological history
Formed by the precipitation of calcium carbonate from cold or hot spring water (travertine) or in caves as flowstone. This specimen is a secondary mineral deposit found in sedimentary environments, often associated with limestone regions.
Uses & applications
Primarily used for ornamental purposes such as decorative carvings, polished towers (obelisks), jewelry (pendants/beads), and internal architectural features like tiling or countertops.
Geological facts
Despite being commercially sold as 'Green Onyx,' it is geologically a form of banded calcite or travertine. True onyx is a variety of chalcedony (quartz) with a hardness of 7, whereas this material is much softer and will react (fizz) if exposed to weak acids.
Field identification & locations
Identify in the field by its distinct parallel banding and soft texture. It can be easily scratched with a steel knife (unlike real onyx). Commonly found in Mexico, Pakistan, Iran, and Turkey. Collectors value it for its translucency when held to light.
More like this
Other sedimentary specimens
Sandstone or Siltstone
Arenite (if sandstone)
Sedimentary
Sandstone
Arenite (primarily SiO2)
sedimentary
Shale or Slaty Mudstone
Argillaceous sedimentary rock
sedimentary
Chert Breccia
Brecciated Chert (Microcrystalline Silica)
sedimentary
Sandstone (Quartz-rich)
Arenite (SiO2)
sedimentary
Sandstone (with man-made markings)
Arenite (composed primarily of Quartz, SiO2)
sedimentary