Limestone Onyx

A variety of banded calcite of stalagmitic origin showing patterns similar to onyx. Often cut and used as a decorative stone. Note: some sources shorten the name to 'onyx'. This is incorrect and confusing and should not be encouraged. True onyx is quartz (hardness 7), this material is much softer (hardness 3) and has very much lower acid resistance.

Structural context

Calcite
Crystal System trigonalCrystal Class hexagonal scalenohedralSpace Group R-3c

Chemical context

Stoichiometric formulas

Limestone Onyx
mindat.org
  • March 13, 2023CaCO3
Calcite
mindat.org
  • March 13, 2023CaCO3
IMA
  • March 13, 2023Ca(CO3)
mineralogy.rocks
  • Aug. 30, 2022CaCO3

Physical properties

ColorColor entities, recognized using a custom trained NER model
                • gray
                Color noteOriginal color note from the source
                White, yellow, red, orange, blue, green, brown, gray etc.
                StreakStreak entities, recognized using a custom trained NER model
                  Streak noteOriginal streak note from the source
                  White
                  Lustre
                  Vitreous
                  Sub-Vitreous
                  Resinous
                  Waxy
                  Pearly
                  Fracture
                  Conchoidal
                  Transparency
                  Transparent
                  Translucent
                  Luminescence
                  Fluorescent
                  Tenacity
                  brittle
                  Hardness
                  3
                  Calculated density
                  2.711