| 词条 | Nioboholtite |
| 释义 |
| name = Nioboholtite | category = Silicate mineral | image = | imagesize = | alt = | caption = | formula = (Nb0.6[]0.4)Al6BSi3O18 | strunz = | dana = | system = Orthorhombic | class = Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m) | symmetry = Pnma | unit cell = a = 47.00, b = 11.83 c = 20.24 [Å] (approximated) | color = Creamy-white to brownish yellow, grey-yellow | colour = | habit = | twinning = | cleavage = | fracture = | tenacity = | mohs = | luster = | streak = White | diaphaneity = Translucent | gravity = | density = | polish = | opticalprop = Biaxal (-) | refractive = nα=1.74-1.75, nβ~1.76, nγ~1.76 (approximated) | birefringence = | pleochroism = | 2V = | dispersion = | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = | impurities = | alteration = | other = | references =[1][2] }}Nioboholtite is an extremely rare mineral with the formula (Nb0.6[]0.4)Al6BSi3O18. It is niobium-rich member of dumortierite supergroup, and 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.[1] Nioboholtite and schiavinatoite are both minerals with essential niobium and boron.[3] AssociationNioboholtite is mainly associated with holtite and a number of other minerals (see szklaryite).[1] Notes on chemistryMain impurities in nioboholtite are antimony and arsenic, with trace or minor aluminium iron, tantalum, titanium, phosphorus and hydroxyl groups.[1] References1. ^1 2 3 {{cite journal|doi=10.1180/minmag.2013.077.6.10 |title=The dumortierite supergroup. II. Three new minerals from the Szklary pegmatite, SW Poland: Nioboholtite, (Nb0.6〈0.4)Al6BSi3O18, titanoholtite, (Ti0.75〈0.25)Al6BSi3O18, and szklaryite, 〈Al6BAs3+3O15 |journal=Mineralogical Magazine |volume=77 |issue=6 |pages=2841 |year=2013 |last1=Pieczka |first1=A. |last2=Evans |first2=R. J. |last3=Grew |first3=E. S. |last4=Groat |first4=L. A. |last5=Ma |first5=C. |last6=Rossman |first6=G. R. }} {{silicate-mineral-stub}}2. ^{{cite web|url=http://www.mindat.org/min-43588.html |title=Nioboholtite: Nioboholtite mineral information and data |website=Mindat.org |accessdate=2016-03-03}} 3. ^{{cite web|url=http://www.mindat.org/min-7110.html |title=Schiavinatoite: Schiavinatoite mineral information and data |website=Mindat.org |accessdate=2016-03-10}} 5 : Silicate minerals|Niobium minerals|Aluminium minerals|Borate minerals|Orthorhombic minerals |
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