Nioboholtite

Nioboholtite
Nioboholtite
General
Category	Silicate mineral
Formula; (repeating unit)	(Nb0.6[]0.4)Al6BSi3O18
IMA symbol	Nhlt
Crystal system	Orthorhombic
Crystal class	Dipyramidal (mmm) ; H-M symbol: (2/m 2/m 2/m)
Space group	Pnma
Unit cell	a = 47.00, b = 11.83 ; c = 20.24 [Å] (approximated)
Identification
Color	Creamy-white to brownish yellow, grey-yellow
Streak	White
Diaphaneity	Translucent
Optical properties	Biaxal (-)
Refractive index	nα=1.74-1.75, nβ~1.76, nγ~1.76 (approximated)
References

Nioboholtite is an extremely rare mineral with the formula (Nb_0.6[]_0.4)Al₆BSi₃O₁₈. It is the niobium-rich member of the dumortierite supergroup, and the niobium analogue of holtite of the holtite group. It is one of three quite recently found minerals of this group, the other two being titanoholtite and szklaryite, all coming from the Szklary village near Ząbkowice Śląskie in Poland. They occur in a unique pegmatite.^[2] Nioboholtite and schiavinatoite are both minerals with essential niobium and boron.^[4]

Association[]

Nioboholtite is mainly associated with and a number of other minerals (see szklaryite).^[2]

Notes on chemistry[]

Main impurities in nioboholtite are antimony and arsenic, with trace or minor aluminium iron, tantalum, titanium, phosphorus and hydroxyl groups.^[2]

References[]

^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85: 291–320.
^ ^a ^b ^c ^d Pieczka, A.; Evans, R. J.; Grew, E. S.; Groat, L. A.; Ma, C.; Rossman, G. R. (2013). "The dumortierite supergroup. II. Three new minerals from the Szklary pegmatite, SW Poland: Nioboholtite, (Nb_0.6〈_0.4)Al₆BSi₃O₁₈, titanoholtite, (Ti_0.75〈_0.25)Al₆BSi₃O₁₈, and szklaryite, 〈Al₆BAs³⁺₃O₁₅". Mineralogical Magazine. 77 (6): 2841. Bibcode:2013MinM...77.2841P. doi:10.1180/minmag.2013.077.6.10. S2CID 51740732.
^ "Nioboholtite: Nioboholtite mineral information and data". Mindat.org. Retrieved 2016-03-03.
^ "Schiavinatoite: Schiavinatoite mineral information and data". Mindat.org. Retrieved 2016-03-10.

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[1] Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85: 291–320.

[MinMag-2] Pieczka, A.; Evans, R. J.; Grew, E. S.; Groat, L. A.; Ma, C.; Rossman, G. R. (2013). "The dumortierite supergroup. II. Three new minerals from the Szklary pegmatite, SW Poland: Nioboholtite, (Nb_0.6〈_0.4)Al₆BSi₃O₁₈, titanoholtite, (Ti_0.75〈_0.25)Al₆BSi₃O₁₈, and szklaryite, 〈Al₆BAs³⁺₃O₁₅". Mineralogical Magazine. 77 (6): 2841. Bibcode:2013MinM...77.2841P. doi:10.1180/minmag.2013.077.6.10. S2CID 51740732.

[Mindat-3] "Nioboholtite: Nioboholtite mineral information and data". Mindat.org. Retrieved 2016-03-03.

[4] "Schiavinatoite: Schiavinatoite mineral information and data". Mindat.org. Retrieved 2016-03-10.

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