# Pabstite

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> Source: https://en.wikipedia.org/wiki/Pabstite
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{{Infobox mineral
| name        = Pabstite
| category    = [Cyclosilicate](/source/Cyclosilicate)
| boxwidth    = 
| boxbgcolor  = 
| image       = Pabstite.jpg
| imagesize   = 
| alt         = 
| caption     = Pabstite
| formula     = {{chem2|Ba(Sn,Ti)Si3O9}}
| IMAsymbol   = Pab<ref>{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|url=https://www.cambridge.org/core/journals/mineralogical-magazine/article/imacnmnc-approved-mineral-symbols/62311F45ED37831D78603C6E6B25EE0A|journal=Mineralogical Magazine|volume=85|issue=3 |pages=291–320|doi=10.1180/mgm.2021.43 |bibcode=2021MinM...85..291W |url-access=subscription}}</ref>
| molweight   = 
| strunz      = 9.CA.05
| dana        = 59.01.01.03
| system      = [Hexagonal](/source/Hexagonal_crystal_system)
| class       = Ditrigonal dipyramidal ({{overline|6}}m2) <br/>[H-M symbol](/source/H-M_symbol): ({{overline|6}} m2)
| symmetry    = ''P''{{overline|6}}c2
| color       = Colorless to white with a pink tinge
| colour      = 
| habit       = Granular anhedral, rare as crystals showing a trigonal outline
| lattice     = 
| twinning    = 
| cleavage    = 
| fracture    = 
| tenacity    =
| mohs        = 6
| luster      = Vitreous
| streak      = 
| diaphaneity = 
| gravity     = 4.03
| density     = 
| polish      = 
| opticalprop = Uniaxial (−)
| refractive  = nω = 1.685 nε = 1.674
| birefringence = δ = 0.011
| pleochroism = 
| 2V          = 
| dispersion  = 
| extinction  = 
| length fast/slow =
| fluorescence= Bluish white under short-wave UV
| absorption  =
| melt        = 
| fusibility  = 
| diagnostic  = 
| solubility  = 
| other       = 
| alteration  = 
| references  = <ref>[https://www.mineralienatlas.de/lexikon/index.php/MineralData?mineral=Pabstite Mineralienatlas]</ref><ref name=Handbook>http://rruff.geo.arizona.edu/doclib/hom/pabstite.pdf Handbook of Mineralogy</ref><ref name=Webmin>http://webmineral.com/data/Pabstite.shtml Webmineral data</ref><ref name=Mindat>http://www.mindat.org/min-3057.html Mindat</ref>
}}

'''Pabstite''' is a [barium](/source/barium) [tin](/source/tin) [titanium](/source/titanium) [silicate mineral](/source/silicate_mineral) that is found in [contact metamorphosed](/source/Contact_metamorphism) [limestone](/source/limestone). It belongs to the [benitoite](/source/benitoite) group of minerals. The chemical formula of pabstite is {{chem2|Ba(Sn,Ti)Si3O9}}. It is found in [Santa Cruz, California](/source/Santa_Cruz%2C_California). The [crystal](/source/crystal) system of the mineral is hexagonal.

== Composition ==
Pabstite is 37.7% SiO<sub>2</sub>, 3.8% TiO<sub>2</sub>, 24.4% SnO<sub>2</sub> and 33.2% BaO.<ref name=Wainwright/> However, Ti and Sn could vary from point to point by approximately ±0.5% TiO<sub>2</sub> and ±1% SnO<sub>2</sub>.  Pabstite is a tin bearing analog of [benitoite](/source/benitoite). Although, (Sn<sup>4+</sup> = 0.71 Å) and (Ti<sup>4+</sup>= 0.68Å) have similar charge and ionic size, it is uncommon to find them substituting each other.

== Geologic occurrence ==

Pabstite commonly occurs as anhedral crystals and masses that vary in their color from colorless to white.<ref name=Dunning>Dunning, G. E & Cooper, J. F. Jr. (1986). "Mineralogy of the Kalkar Quarry, Santa Cruz, California." '' Mineralogical Record, 17'', 315- 326.</ref> They produce a pink tinge when they are freshly broken.  Large amounts of pabstite were found in Santa Cruz as fracture filling and disseminated grains in recrystallized siliceous limestones.<ref name=Wainwright>Wainwright, John E. N & Evans, Bernard W. (1965). "Pabstite,<sup>1</sup> the tin analogue of benitoite."  ''The American Mineralogist, 50'', 1164–1169.</ref>  This is geologic evidence of contact [metamorphism](/source/metamorphism). In addition, pabstite can be found in Rush Creek in California when benitoite contains small amounts of tin. It is commonly occurs in rocks that contain [calcite](/source/calcite), [quartz](/source/quartz), [tremolite](/source/tremolite), [witherite](/source/witherite), [phlogopite](/source/phlogopite), [diopside](/source/diopside), minor amounts of [forsterite](/source/forsterite) and [taramellite](/source/taramellite). Pabstite can also be found associated with [galena](/source/galena), [cassiterite](/source/cassiterite) and [sphalerite](/source/sphalerite).<ref name=Dunning/>

== Structure ==

Pabstite is considered the tin analog of benitoite.<ref name=Wainwright/> It has a hexagonal crystal system with a P6*2C space group. Its dimensions are as follows, a= 6.7037(7), c= 9.824(1) Å3, C= 382.3(1) Å3, Z=2. Pabstite has the structure of the benitoite group of minerals.<ref name=Hawthorne>Hawthorne, Frank C. (1987).  The crystal chemistry of the benitoite group minerals and structural relations in (Si<sub>3</sub>O<sub>9</sub>) ring 
structures.  ''Neues Jahrbuch fuer Mineralogie.  Monatshefte. 1987'', 16–30.</ref> In the structure of pabstite, there are four oxygens surrounding the cations in a pseudo-tetrahedral arrangement. A three-membered [cyclosilicate](/source/cyclosilicate) ring (Si<sub>3</sub>O<sub>9</sub>) is formed by repeating the tetrahedron using space group symmetry. Quadrivalent [cations](/source/cations) connect the rings to form a three-dimensional framework. Since the silicate rings have a geometry that is identical in all directions, a solid rigid unit is formed in the structure. In a distorted hexagonal antiprism arrangement, Ba, which has a high symmetry, is bounded by 12 oxygens. Two different BaـــO distances are present. [M<sup>4+</sup> Si<sup>3</sup>O<sup>9</sup>] frameworks are connected by Ba cations which lead to a poor [cleavage](/source/Cleavage_(crystal)).

== Physical properties ==
Finding pabstite in the field is hard and rare.<ref name=Dunning/> When using a shortwave [ultraviolet light](/source/ultraviolet_light), bluish white fluorescence is revealed from the specimens. This property is commonly used to identify pabstite. Pabstite is colorless to white. The diameter of pabstite grains is usually less than 2&nbsp;mm and they contain minute [fluid](/source/Fluid_inclusions) and solid [inclusions](/source/Inclusion_(mineral)). Its hardness is 6 on [Mohs scale of mineral hardness](/source/Mohs_scale_of_mineral_hardness).<ref name=Wainwright/> Its density is 4.03 g/cm<sup>3</sup> and it is uniaxial. The interference colors of pabstite are anomalous blue-violet and golden yellow. The [refractive indices](/source/refractive_index) of pabstite are ω = 1.685±0.002 and ε = 1.674±0.002 which result in low [birefringence](/source/birefringence) and absent [dichroism](/source/dichroism).

== Discovery and locations ==
Pabstite was first discovered in 1965 for an occurrence in the Kalkar quarry of Santa Cruz County, California.  The mineral was named for [Adolf Pabst](/source/Adolf_Pabst) (1899–1990) a mineralogy professor at the [University of California, Berkeley](/source/University_of_California%2C_Berkeley).<ref name=Handbook/><ref name=Mindat/>

Pabstite has also been reported from Tres Pozos, [Baja California Norte](/source/Baja_California_Norte), [Mexico](/source/Mexico) and the Alai Range of the [Tien Shan Mountains](/source/Tien_Shan_Mountains) in [Tajikistan](/source/Tajikistan).<ref name=Mindat/>

== References ==
{{reflist}}

Category:Geology of California
Category:Cyclosilicates
Category:Barium minerals
Category:Tin minerals
Category:Titanium minerals
Category:Hexagonal minerals
Category:Minerals in space group 188

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Adapted from the Wikipedia article [Pabstite](https://en.wikipedia.org/wiki/Pabstite) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Pabstite?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.