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, 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.
