Celestine is a strontium sulfate mineral best known for its stunning, pale sky-blue crystals found in sedimentary vugs and geodes. Collectors typically look for its characteristic orthorhombic tabular habits, often associated with calcitic or dolomitic matrix.
Is this celestine?
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 celestine with a known reference. Celestine sits at Mohs 3-3.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Celestine leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Celestine typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: colorless, white, pale blue, blue, gray.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: tabular, prismatic, or pyramidal crystals, often in geodes.
Often confused with
Celestine vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside celestine
Minerals reported to co-occur with celestine. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- SrSO₄
- Mohs hardness
- 3-3.5
- Density
- 3.95-3.97 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Tabular, Prismatic, Or Pyramidal Crystals, Often in Geodes
- Cleavage
- Perfect in One Direction
- Fluorescence
- None to Faint Blue Under UV
- Rarity
- Common
- Uses
- Collector, Decorative, Industrial Source of Strontium
- Host rock
- Sedimentary Limestones and Evaporite Deposits
- Typical price
- $10-50 for small clusters, $100-500+ for large exhibition geodes
Where rockhounds find celestine
3 mapped spotsClassic worldwide localities
- Madagascar
- United States (Ohio)
- Mexico
- Italy
- Poland
Field-hunting tip
Look in sedimentary limestones and evaporite deposits country — that is the host setting where celestine typically forms. If you start seeing calcite, sulfur, fluorite in float, you are in the right ground. Field specimens usually show a tabular, prismatic, or pyramidal crystals, often in geodes habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Connecticut, Pennsylvania, Wisconsin — start trip planning there.
Common questions
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Find celestine on the map
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