Image: <a rel="nofollow" class="external text" href="https://www.flickr.com/people/47445767@N05">James St. John</a> (CC BY 2.0)
trigonalcommoncarbonates
Onyx (Calcite variety)
CaCO3
A large, whitish, banded dripstone formation, characteristic of travertine, exhibiting translucent layers and a smooth, polished appearance.
Onyx (Calcite variety) Physical Properties
Mohs Hardness
3Crystal System
trigonalLuster
vitreousStreak Color
whiteCleavage
perfect rhombohedralFracture
conchoidal to unevenSpecific Gravity
2.71Colors
white, cream, brown, green, pinkTransparency
translucentType Locality
Crystal Onyx Cave, near Cave City, Kentucky, USAMineral Group
carbonatesUses
decorative stone, carvings, countertops, architectural materialAssociated Minerals
limestone, dolostoneRarity
commonGeological Context
This onyx, a form of travertine composed of calcite, forms in caves through the precipitation of calcium carbonate from mineral-rich water. It is found in a Tertiary-Quaternary cave environment, specifically in Crystal Onyx Cave, Kentucky, where the cave walls are limestone and dolostone.
