# Gonnardite

> Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Gonnardite
> Markdown URL: https://mediated.wiki/source/Gonnardite.md
> Source: https://en.wikipedia.org/wiki/Gonnardite
> Source revision: 1331288742
> License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/)

{{Short description|Zeolite mineral}}
{{Infobox mineral
| name = Gonnardite
| category = [Tectosilicate](/source/Tectosilicate) minerals
| group = [Zeolite](/source/Zeolite) group, [natrolite](/source/natrolite) subgroup
| image = gonnardite.jpg
| imagesize   = 260px
| caption = Gonnardite from the Bundoora Quarry, [Victoria, Australia](/source/Victoria%2C_Australia).  Specimen size 4.9 cm
| formula = (Na,Ca)<sub>2</sub>(Si,Al)<sub>5</sub>O<sub>10</sub>·3H<sub>2</sub>O
| IMAsymbol   = Gon<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 =
| strunz = 9.GA.05 (10 ed) <br /><small>8/J.21-40 (8 ed)</small>
| dana = 77.1.5.7
| system = [Tetragonal](/source/Tetragonal)
| class = Scalenohedral ({{overline|4}}2m) <br />[H-M symbol](/source/H-M_symbol): ({{overline|4}} 2m)
| symmetry = ''I''{{overline|4}}2d
| unit cell = a = 13.38 <br />c = 6.66&nbsp;[Å]; Z&nbsp;=&nbsp;2
| color = Colorless, white, yellow or pink to salmon orange
| habit = Radiating fibrous; massive
| twinning = 
| cleavage =
| fracture =
| tenacity =
| mohs = 4 to 5
| luster = Vitreous to silky or dull
| refractive = n<sub>α</sub> = 1.514, n<sub>β</sub> = 1.515, n<sub>γ</sub> = 1.520
| opticalprop = Biaxial (+)   
| 2V   = Measured, 52°
| birefringence = δ = 0.006
| pleochroism =
| streak = White
| gravity = 2.21 to 2.36
| density =
| melt =
| fusibility =
| diagnostic =
| solubility =
| diaphaneity = Translucent
| other = 
| references = <ref name=Mindat>{{Cite web|url=http://www.mindat.org/min-1724.html|title = Gonnardite}}</ref><ref name=Webmin>{{Cite web|url=http://www.webmineral.com/data/Gonnardite.shtml|title = Gonnardite Mineral Data}}</ref><ref name=HOM>{{cite web |last1=Anthony |first1=John W. |last2=Bideaux |first2=Richard A. |last3=Bladh |first3=Kenneth W. |last4=Nichols |first4=Monte C. |title=Gonnardite |url=http://www.handbookofmineralogy.org/pdfs/gonnardite.pdf |website=Handbook of Mineralogy |publisher=Mineral Data Publishing |access-date=13 March 2022 |date=2005}}</ref><ref name=Dana>Gaines et al (1997) Dana's New Mineralogy, Wiley</ref> }}

'''Gonnardite''' is a comparatively rare, fibrous [zeolite](/source/zeolite), [natrolite](/source/natrolite) subgroup.  Older papers claim that a complete solid solution exists between tetranatrolite and gonnardite, but tetranatrolite was discredited as a separate species in 1999.<ref name=AM84>American Mineralogist (1999) 84: 1445–1450</ref> A series, based on the disorder of the silicon-aluminum in the framework, appears to exist between Na-rich gonnardite and natrolite, Na<sub>2</sub>(Si<sub>3</sub>Al<sub>2</sub>)O<sub>10</sub>·2H<sub>2</sub>O.<ref name=ZOW>Tschernich, Zeolites of the World (1992) Geoscience Press, pages 215 to 225</ref>

Gonnardite was named in 1896 after Ferdinand Pierre Joseph Gonnard<ref name=GON>{{Cite web |url=http://www.minrec.org/labels.asp?colid=1316 |title=Archived copy |access-date=2010-03-30 |archive-date=2014-07-29 |archive-url=https://web.archive.org/web/20140729151344/http://www.minrec.org/labels.asp?colid=1316 |url-status=dead }}</ref> (1833–1923), who was Professor of Mining Engineering at the University of Lyon, France.

==Crystallography==
[Orthorhombic](/source/Orthorhombic)-bipyramidal class 2/m 2/m 2/m and [tetragonal](/source/tetragonal)-scalenoidal class {{Overline|4}}2m (orthorhombic with a very close to b, or tetragonal with a equal to b). <br />Unit Cell Parameters: a = b = 13.21&nbsp;Å, c = 6.622&nbsp;Å, Z = 2<ref name=Webmin/><ref name=HOM/><ref name=MM62>Mineralogical Magazine (1998) 62: 548</ref><br />Space Group: I{{Overline|4}}2d

==Crystal habit==
Crystals are [prismatic](/source/Prism_(geometry)), bounded by {110} and {111} as well as {100} and {001},<ref name=ZOW/> and gonnardite also occurs as radial hemispheres. Commonly found as zoned prisms or [aggregate](/source/Aggregate_(geology))s with [thomsonite](/source/thomsonite), [natrolite](/source/natrolite) and [paranatrolite](/source/paranatrolite).<ref name=ZOW/>

==Structure==
Gonnardite is a [tectosilicate](/source/tectosilicate) belonging to the natrolite group. The natrolite minerals are composed of chains of AlO<sub>4</sub> and SiO<sub>4</sub> [tetrahedra](/source/tetrahedra) that link to form frameworks.  As with all zeolites, there are channels within the framework, and for the natrolite minerals the channels are occupied by [polyhedra](/source/polyhedra) containing [sodium](/source/sodium), [calcium](/source/calcium) or [barium](/source/barium), together with oxygen and water.<ref name=AM77>American Mineralogist (1972) 77:685</ref> Gonnardite has the same framework structure as natrolite, but a disordered Si, Al distribution on the tetrahedral sites.<ref name=MM62/> Some of the water sites in the disordered natrolite structure of gonnardite are empty.<ref name=ZOW/>

==Environment==
Gonnardite has been found in silica-poor volcanics and [pegmatites](/source/pegmatites).  It occurs with [thomsonite](/source/thomsonite) and [natrolite](/source/natrolite) in [vesicle](/source/Vesicular_texture)s in the [volcanic rock](/source/volcanic_rock) of The Nut, near [Stanley, Tasmania](/source/Stanley%2C_Tasmania), Australia, intergrown with [natrolite](/source/natrolite) at Don Hill, Tasmania and in drill holes with [chabazite](/source/chabazite) and [calcite](/source/calcite) near Guildford, Tasmania.<ref name=AJM>Australian Journal of Mineralogy (2004) 10-2: 59–72</ref>  It is also found in [nepheline-syenite](/source/nepheline-syenite) in the [Grenville Geological Province](/source/Grenville_Orogeny), which is part of the [Canadian Shield](/source/Canadian_Shield).<ref name=MinRec>The Mineralogical Record 37-4: 285</ref>
The [type locality](/source/type_locality_(geology)) (the place where the mineral was first described) is La Chaux de Bergonne, [Gignat](/source/Gignat), Saint-Germain-Lembron, Puy-de-Dôme, [Auvergne](/source/Auvergne_(region)), France, and [type material](/source/Type_specimen_(mineralogy)) from this locality is held at the [Natural History Museum, London](/source/Natural_History_Museum%2C_London), England, registration number BM.1930,166.

==References==

{{Reflist}}

{{Commons}}

Category:Natrolite subgroup
Category:Tetragonal minerals
Category:Minerals in space group 122

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