Fossil coral is marine coral that has been replaced by silica, preserving the original structure of the organism. Collectors look for intricate, flower-like patterns in cross-sections, which become highly visible when the material is polished.
Is this fossil 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 fossil coral with a known reference. Fossil Coral sits at Mohs 6.5-7, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Fossil Coral leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Fossil Coral typically shows a waxy luster.
- 4Match the color rangeCompare against the expected color range: white, tan, brown, red, pink, gray.
- 5Look at form & habitCrystal system: trigonal. Typical habit: massive.
Often confused with
Fossil Coral vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside fossil coral
Minerals reported to co-occur with fossil coral. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- SiO₂
- Mohs hardness
- 6.5-7
- Density
- 2.6-2.7 g/cm³
- Streak
- White
- Luster
- Waxy
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Massive
- Cleavage
- None
- Rarity
- Common
- Uses
- Lapidary, Collector, Decorative, Jewelry
- Host rock
- Sedimentary Strata
- Typical price
- $5-50 for cabs and specimens, $100+ for large polished displays
Where rockhounds find fossil coral
1 mapped spotsClassic worldwide localities
- Florida, USA
- Indonesia
- Utah, USA
- Thailand
- Georgia, USA
Field-hunting tip
Look in sedimentary strata country, the host setting where fossil coral typically forms. If you start seeing quartz, calcite, pyrite in float, you are in the right ground. Field specimens usually show a massive habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Florida. Start trip planning there.
Common questions
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Find fossil coral on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
