Calcite nodules are rounded, spherical, or irregular accretions of calcite that form within sedimentary host rocks. Collectors prize them for their interesting shapes and often spectacular fluorescence under ultraviolet light.
Is this calcite nodules?
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 calcite nodules with a known reference. Calcite Nodules sits at Mohs 3 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Calcite Nodules leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Calcite Nodules typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, yellow, gray, brown, colorless.
- 5Look at form & habitCrystal system: trigonal. Typical habit: botryoidal, massive, nodular.
Often confused with
Calcite Nodules vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside calcite nodules
Minerals reported to co-occur with calcite nodules. 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
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Botryoidal, Massive, Nodular
- Cleavage
- Perfect Rhombohedral
- Fluorescence
- Often Bright Pink or Red Under SW UV
- Rarity
- Common
- Uses
- Collector, Decorative
- Host rock
- Sedimentary Limestone or Shale
- Typical price
- $5-30 for small nodules, $50-200 for large display pieces
Where rockhounds find calcite nodules
1 mapped spotsClassic worldwide localities
- Missouri, USA
- Kansas, USA
- Oklahoma, USA
- Mexico
- Germany
Field-hunting tip
Look in sedimentary limestone or shale country — that is the host setting where calcite nodules typically forms. If you start seeing quartz, pyrite, galena in float, you are in the right ground. Field specimens usually show a botryoidal, massive, nodular habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Missouri — start trip planning there.
Common questions
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Find calcite nodules on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
