Simpsonite is a rare aluminum tantalum oxide mineral typically found in highly evolved granite pegmatites. Collectors look for its characteristic yellowish, prismatic crystals which often display a distinct bright yellow fluorescence under shortwave ultraviolet light.
Is this simpsonite?
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 simpsonite with a known reference. Simpsonite sits at Mohs 6-7 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Simpsonite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Simpsonite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: yellow, brown, colorless, white.
- 5Look at form & habitCrystal system: trigonal. Typical habit: prismatic crystals, massive.
Often confused with
Simpsonite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside simpsonite
Minerals reported to co-occur with simpsonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Al₄Ta₃O₁₃(OH)
- Mohs hardness
- 6-7
- Density
- 6.7-6.9 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Prismatic Crystals, Massive
- Cleavage
- None
- Fluorescence
- Bright Yellow Under SW UV
- Rarity
- Rare
- Uses
- Collector, Ore of Tantalum
- Host rock
- Granite Pegmatites
- Typical price
- $50-500 thumbnail
Where rockhounds find simpsonite
Classic worldwide localities
- Bikita, Zimbabwe
- Western Australia
- Paraíba, Brazil
Field-hunting tip
Look in granite pegmatites country — that is the host setting where simpsonite typically forms. If you start seeing tantalite, cassiterite, albite in float, you are in the right ground. Field specimens usually show a prismatic crystals, massive habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find simpsonite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
