Alstonite is a rare barium-calcium carbonate that frequently forms complex pseudo-hexagonal twinned crystals. Collectors primarily find it in low-temperature hydrothermal veins, where it is often associated with witherite and fluorite. It is best identified by its distinct fluorescence and its typical twinning habits which create triangular striations on crystal faces.
Is this alstonite?
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 alstonite with a known reference. Alstonite sits at Mohs 4-4.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Alstonite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Alstonite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: colorless, white, gray, pale yellow.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: pseudo-hexagonal dipyramidal crystals, twinning often mimics hexagonal prisms.
Often confused with
Alstonite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside alstonite
Minerals reported to co-occur with alstonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaBa(CO₃)₂
- Mohs hardness
- 4-4.5
- Density
- 3.72 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Pseudo-hexagonal Dipyramidal Crystals, Twinning Often Mimics Hexagonal Prisms
- Cleavage
- Distinct
- Fluorescence
- Bright White or Yellow Under SW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Veins in Sedimentary Host Rocks
- Typical price
- $20-150 thumbnail
Where rockhounds find alstonite
1 mapped spotsClassic worldwide localities
- Alston Moor, Cumbria, England
- Cave-in-Rock, Illinois, USA
- Langban, Sweden
Field-hunting tip
Look in hydrothermal veins in sedimentary host rocks country — that is the host setting where alstonite typically forms. If you start seeing witherite, calcite, galena in float, you are in the right ground. Field specimens usually show a pseudo-hexagonal dipyramidal crystals, twinning often mimics hexagonal prisms habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Illinois — start trip planning there.
Common questions
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Find alstonite on the map
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