Cave pearls are small, rounded, spherical or ovoid concretions of calcite that form in limestone caves through the deposition of calcium carbonate around a nucleus. They are typically found in shallow cave pools where dripping water keeps the pearls in constant motion, preventing them from cementing to the pool floor.

Hardness

Mohs

Luster

Dull

Streak

White

Transparency

Opaque

mineralcommonCalcite family

Cave Pearls

Hardness: 3
Luster: Dull
Streak: White
Transparency: Opaque

Is this cave pearls?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch cave pearls with a known reference. Cave Pearls sits at Mohs 3 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Cave Pearls leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Cave Pearls typically shows a dull luster.
4
Match the color range
Compare against the expected color range: white, cream, gray, brown.
5
Look at form & habit
Crystal system: trigonal. Typical habit: spherical or ovoid concretionary aggregates.

Often found alongside cave pearls

Minerals reported to co-occur with cave pearls. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: CaCO₃
Mohs hardness: 3
Density: 2.71 g/cm³
Colors: White Cream Gray Brown
Streak: White
Luster: Dull
Transparency: Opaque
Crystal system: Trigonal
Crystal habit: Spherical or Ovoid Concretionary Aggregates
Cleavage: Perfect Rhombohedral
Fluorescence: Often Exhibits White or Yellow Under UV
Rarity: Common
Uses: Collector, Educational
Host rock: Limestone Solution Caves
Typical price: $10-100 per specimen depending on size and luster

Where rockhounds find cave pearls

Classic worldwide localities

Carlsbad Caverns, USA
Lechuguilla Cave, USA
Postojna Cave, Slovenia
Grutas de Cacahuamilpa, Mexico

Field-hunting tip

Look in limestone solution caves country — that is the host setting where cave pearls typically forms. If you start seeing calcite, aragonite in float, you are in the right ground. Field specimens usually show a spherical or ovoid concretionary aggregates habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify cave pearls?+

Mohs hardness is 3. It typically shows a dull luster. The streak is white. Common colors include white, cream, gray, brown.

Where is cave pearls found?+

Notable localities include Carlsbad Caverns, USA; Lechuguilla Cave, USA; Postojna Cave, Slovenia; Grutas de Cacahuamilpa, Mexico.

How much is cave pearls worth?+

Typical asking prices fall in the range of $10-100 per specimen depending on size and luster. Quality, size, and provenance can move individual specimens well outside that range.

What minerals are found with cave pearls?+

Cave Pearls commonly co-occurs with Calcite, Aragonite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does cave pearls form in?+

Cave Pearls typically forms in limestone solution caves. Working float back to the host body is the standard way to chase a fresh occurrence.

What is cave pearls used for?+

Cave Pearls is used in collector, educational.

Find cave pearls on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.