Coral consists of the skeletal remains of colonial marine organisms primarily composed of calcium carbonate. Collectors often seek out branching or botryoidal structures, which can be polished to a high luster for jewelry. Note that modern coral harvesting is often restricted to protect reef ecosystems, making vintage specimens highly valued.
Is this coral?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch coral with a known reference. Coral sits at Mohs 3-4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Coral leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Coral typically shows a dull to waxy luster.
- 4Match the color rangeCompare against the expected color range: white, pink, red, orange, brown.
- 5Look at form & habitTypical habit: branching, massive, or columnar.
Often confused with
Coral vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside coral
Minerals reported to co-occur with coral. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaCO₃
- Mohs hardness
- 3-4
- Density
- 2.6-2.7 g/cm³
- Streak
- White
- Luster
- Dull to Waxy
- Transparency
- Opaque
- Crystal habit
- Branching, Massive, Or Columnar
- Cleavage
- None
- Rarity
- Common
- Uses
- Jewelry, Lapidary, Decorative
- Host rock
- Marine Sedimentary Deposits
- Typical price
- $10-100 per specimen
Where rockhounds find coral
4 mapped spotsClassic worldwide localities
- Mediterranean Sea
- Japan
- Taiwan
- Red Sea
- Australia
Field-hunting tip
Look in marine sedimentary deposits country, the host setting where coral typically forms. If you start seeing calcite, aragonite in float, you are in the right ground. Field specimens usually show a branching, massive, or columnar habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Florida, Iowa, Texas. Start trip planning there.
More coral photos
Common questions
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Find coral on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
