Where is Calcite found?
Calcite (Calcium Carbonate)
Got a photo? Identify rocks instantly with the Rockby app
Open the appCalcite occurs in specific geological environments. Knowing where to look, and in what kind of rock, is the difference between going home empty-handed and finding a great specimen.
Where to find Calcite
Carlsbad Caverns, New Mexico, USA
Famous for spectacular speleothems (stalactites, stalagmites, flowstone) composed primarily of calcite.
Iceland
Historically known for large, clear crystals of 'Iceland spar' (optical calcite) used in polarizing optics.
Elmwood Mine, Tennessee, USA
Produces world-class, large, gemmy, golden-yellow calcite crystals, often associated with fluorite and sphalerite.
Mexico (various localities)
Known for diverse and aesthetic calcite specimens, including dogtooth spar and nailhead spar.
Worldwide in limestone and marble quarries
Calcite is the primary mineral in these rocks, found in massive and crystalline forms.
Collecting tips
- Acid Test. Calcite effervesces vigorously (produces bubbles of CO2 gas) when a drop of dilute hydrochloric acid (HCl) is applied. This is a definitive test. Dolomite will only effervesce if powdered.
- Cleavage Recognition. Look for the characteristic perfect rhombohedral cleavage, which produces fragments with parallel faces and angles of approximately 75° and 105°.
- Hardness Test. Calcite has a Mohs hardness of 3, meaning it can be scratched by a copper coin (hardness ~3.5) but will scratch a fingernail (hardness ~2.5). This distinguishes it from harder minerals like quartz (hardness 7) and softer minerals like gypsum (hardness 2).
- Double Refraction. Clear varieties of calcite (Iceland spar) exhibit strong double refraction, where a single line viewed through the crystal appears as two lines.
Quick Check
- Color:
- White, colorless, or various tints
- Luster:
- Vitreous to pearly
- Streak:
- White
Explore Calcite
Identify rocks anywhere
Free on iOS, Android, and Web. Photo identification, full database, and your personal collection.