Simpsonite
A variety of Minerals
What is Simpsonite?
Simpsonite has a general formula of Al4(Ta,Nb)3O13(OH). It occurs as euhedral to subhedral tabular to short and prismatic crystals, commonly in subparallel groups. Under the petrographic microscope it has a very high relief. Discovered in 1938, it was named after Edward Sydney Simpson (1875–1939), government mineralogist and analyst of Western Australia. It is an accessory mineral in some tantalum-rich granite pegmatites. It occurs in association with tantalite, manganotantalite, microlite, tapiolite, beryl, spodumene, montebrasite, pollucite, petalite, eucryptite, tourmaline, muscovite and quartz. It is found in a few locations around the world, notably in the Onca and Paraiba mines of Rio Grande do Norte, Brazil and at Tabba Tabba, Western Australia.
Optical Properties
- Refractive Index
- 1.994-2.040
- Birefringence
- 0.046
- Pleochroism
- None
- Optical Character
- Uniaxial negative
Market Value Factors
Pricing varies for every rock and mineral, so use these universal factors to gauge Simpsonite before comparing listings or appraisals.
Size & Weight
Larger, intact specimens usually command higher prices.
Rarity & Demand
Scarce material or popular varieties sell at a premium.
Condition & Finish
Chips, repairs, and heavy wear lower value; clean prep helps.
Treatment & Provenance
Untreated specimens with documented locality are prized.
Simpsonite Localities Map
See where Simpsonite is found with a localities map, collecting zones, and geology context. Generate a sample map preview below.
Quick Facts
Physical Properties
- Color
- Yellow, light brown, colourless, gray
- Hardness (Mohs)
- 7 - 7.5
- Density
- 6.35 g/cm³
- Streak
- white
Chemical Properties
- Chemical Formula
- Al4Ta3O13(OH)
- Elements
- Al, H, O, Ta
Also Known As
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Simpsonite FAQs
How do I identify Simpsonite?
Simpsonite can be identified by its hardness of 7 - 7.5 on the Mohs scale, Yellow color. Look for these key characteristics when examining specimens.
What color is Simpsonite?
Simpsonite typically appears in Yellow, light brown, colourless, gray. Color can vary depending on impurities and formation conditions.
How hard is Simpsonite?
Simpsonite has a hardness of 7 - 7.5 on the Mohs scale. This makes it a relatively hard mineral suitable for jewelry.
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