Mineral
Banded Calcite / Fluorite (or Onyx/Agate depending on hardness)
CaCO3 or CaF2 (depending on exact ID)
AI-generated identification · may be incorrectTranslucent, banded, vitreous luster. If calcite: Mohs hardness 3, perfect rhombohedral cleavage. If fluorite: Mohs hardness 4, octahedral cleavage. Colors can range from white, cream, brown, to dark grey/black.
Identified More mineral →
Explore Banded Calcite / Fluorite (or Onyx/Agate depending on hardness) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Translucent, banded, vitreous luster. If calcite: Mohs hardness 3, perfect rhombohedral cleavage. If fluorite: Mohs hardness 4, octahedral cleavage. Colors can range from white, cream, brown, to dark grey/black.
Formation & geological history
Formed through precipitation from aqueous solutions, often in veins or hot spring deposits. Can form over various geological periods.
Uses & applications
Often used for carving, lapidary arts, ornamental objects, and jewelry (cabochons, pendants).
Geological facts
Banded varieties are sometimes commercially sold as 'onyx' or 'marble' in the lapidary trade, though geologically they are often banded calcite.
Field identification & locations
Identify by hardness testing (can it be scratched by a steel nail?), acid test (effervesces with drop of dilute HCl if calcite), and banding patterns.
More like this
Other mineral specimens
Gneiss or Schist
Gneiss or Mica Schist with Garnet
Metamorphic
Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
Tumbled granite
Granite, a coarse-grained felsic intrusive igneous rock
igneous
Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
metamorphic
Pegmatite with Tourmaline and Quartz
Igneous Pegmatite
igneous
Granite
Granite (Phaneritic intrusive igneous rock)
igneous