{{Infobox mineral | name = Simpsonite | category = Oxide minerals | boxwidth = | boxbgcolor = #fac561 | image = Simpsonite-154999.jpg | imagesize = 300px | caption = Locality: Alto do Giz pegmatite, Rio Grande do Norte, Brazil. Size: 1.6 × 1.5 × 1.8 cm. | formula = {{chem2|Al4(Ta,Nb)3O13(OH)}} | IMAsymbol = Spn<ref>{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}</ref> | molweight = 813.65 g/mol | strunz = 4.DC.10 | system = Trigonal | class = Pyramidal (3) <br/>H-M symbol: (3) | symmetry = ''P3'' | unit cell = a = 7.37, c = 4.51&nbsp;[Å]; Z&nbsp;=&nbsp;1 | color = White to cream, yellow to yellow-brown when altered | habit = Euhedral, prismatic, striated | twinning = | cleavage = None | fracture = Conchoidal | tenacity = Brittle | mohs = 7–7.5 | luster = Vitreous to adamantine | refractive = n<sub>ω</sub> = 2.045 n<sub>ε</sub> = 2.025 | opticalprop = Uniaxial negative | birefringence = δ = 0.020 | pleochroism = | streak = White | gravity = 6.7 | density = | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = Semitransparent | other = Blue-white cathodoluminescence and yellow fluorescence in SW UV | references = <ref name=HBM>[http://rruff.geo.arizona.edu/doclib/hom/simpsonite.pdf Handbook of Mineralogy]</ref><ref name=Webmin>[http://www.webmineral.com/data/Simpsonite.shtml Webmineral data]</ref><ref name=Mindat>[http://www.mindat.org/min-3670.html Simpsonite: Mindat.org]</ref><ref>Philonen, P.C., Grew, E.S., Ercit, T.S., Roberts, A.C., Jambor, J.L. (2005) New mineral names. American Mineralogist, 90, 1227–1233</ref> }}

'''Simpsonite''' has a general formula of {{chem2|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.<ref name=Mindat/> 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.<ref name=HBM/> It is found in a few locations around the world, notably in the Onca and Paraíba mines of Rio Grande do Norte, Brazil and at Tabba Tabba, Western Australia.<ref name=HBM/>

== References == {{Reflist}}

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Category:Aluminium minerals Category:Oxide minerals Category:Tantalum minerals Category:Niobium minerals Category:Trigonal minerals Category:Minerals in space group 143 Category:Minerals described in 1938