Slawsonite is a rare strontium-bearing feldspar that is primarily valued by mineral collectors for its strong blue fluorescence under short-wave UV light. It is typically found as small, clear to white tabular crystals embedded in metamorphosed limestone or calcium-rich silicate rocks.
Is this slawsonite?
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 slawsonite with a known reference. Slawsonite sits at Mohs 6 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Slawsonite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Slawsonite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: colorless, white, gray.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular crystals.
Often confused with
Slawsonite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside slawsonite
Minerals reported to co-occur with slawsonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- SrAl₂Si₂O₈
- Mohs hardness
- 6
- Density
- 2.79 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular Crystals
- Cleavage
- Perfect On {001} and {010}
- Fluorescence
- Strong Blue Under SW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Metamorphosed Limestone
- Typical price
- $50-500 depending on specimen size and clarity
Where rockhounds find slawsonite
Classic worldwide localities
- Grenville Province, Ontario, Canada
- Khibiny Massif, Russia
- Sar-e-Sang, Afghanistan
Field-hunting tip
Look in metamorphosed limestone country — that is the host setting where slawsonite typically forms. If you start seeing calcite, diopside, grossular in float, you are in the right ground. Field specimens usually show a tabular crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find slawsonite on the map
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