Editing Cristobalite (section)

{{short description|Silica mineral, polymorph of quartz}}
{{Infobox mineral
| name = Cristobalite
| category = [[Tectosilicates]], [[quartz]] [[Mineral group|group]]
| boxwidth = 
| boxbgcolor =
| image = Cristobalite-Fayalite-40048.jpg
| caption = Cristobalite [[spherulite]]s formed by [[devitrification]] from the [[obsidian]] [[matrix (geology)|matrix]].<br />{{small|Specimen from California, US; size: {{cvt|5.9|×|3.8|×|3.8|cm|in}}.}}
| formula = {{chem2|SiO2}}
| IMAsymbol=Crs<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 = 4.DA.15
| dana = 75.1.1.1
| system = [[tetragonal crystal system|Tetragonal]]
| class = [[trapezohedron|Trapezohedral]] (422)
| symmetry  = ''P''4<sub>1</sub>2<sub>1</sub>2,  ''P''4<sub>3</sub>2<sub>1</sub>2
| unit cell = ''a'' = 4.9709(1)&nbsp;Å, <br />''c'' = 6.9278(2)&nbsp;Å; <br />''Z''&nbsp;=&nbsp;4 (α polytype)
| color = Colorless, white
| habit = [[octahedron|Octahedra]] or [[spherulite]]s up to several cm in diameter
| twinning = on {111}
| cleavage = 
| fracture = [[conchoidal fracture|Conchoidal]]
| tenacity = [[brittleness|Brittle]]
| mohs = 6–7
| luster = Vitreous
| refractive = ''n''<sub>ω</sub> = 1.487 <br />''n''<sub>ε</sub> = 1.484
| opticalprop = Uniaxial (−)
| birefringence = 0.003
| pleochroism = None
| streak = White
| gravity = 2.32–2.36
| density =
| melt = {{cvt|1713|C|F}} (β)<ref name=Deer>{{cite book |last1=Deer|first1=W. A. |first2=R. A.|last2=Howie |first3=J.|last3=Zussman |title=An Introduction to the Rock Forming Minerals |publisher=[[Longman]] |year=1966 |pages=340–355 |isbn=0-582-44210-9}}</ref>
| fusibility =
| diagnostic =
| solubility = 
| diaphaneity = Transparent
| other = 
| references = <ref>[https://mineralienatlas.de/lexikon/index.php/MineralData?mineral=Cristobalite Mineralienatlas].</ref><ref name=Handbook>[https://rruff.info/doclib/hom/cristobalite.pdf Cristobalite] {{Webarchive|url=https://web.archive.org/web/20100715214929/http://rruff.geo.arizona.edu/doclib/hom/cristobalite.pdf |date=2010-07-15 }}. Handbook of Mineralogy.</ref><ref name=Mindat>[https://mindat.org/min-1155.html Cristobalite]. Mindat.</ref><ref name=Webmin>{{cite web|url=https://webmineral.com/data/Cristobalite.shtml|title=Cristobalite Mineral Data|website=Webmineral}}</ref>
| SMILES = O[Si]3(O)O[Si](O)(O[Si]4(O)O)O[Si](O)(O)O[Si](O0)(O)O[Si]1(O)O[Si]5(O3)O[Si]2(O)O[Si](O4)(O)O[Si]0(O)O[Si](O)(O)O[Si](O)(O[Si](O)(O)O1)O[Si](O)(O2)O[Si](O)(O)O[Si](O)(O)O[Si](O)(O)O5
| Jmol = O[Si]3(O)O[Si](O)(O[Si]4(O)O)O[Si](O)(O)O[Si](O0)(O)O[Si]1(O)O[Si]5(O3)O[Si]2(O)O[Si](O4)(O)O[Si]0(O)O[Si](O)(O)O[Si](O)(O[Si]6(O)O1)O[Si](O)(O2)O[Si](O)(O)O[Si](O)(O[Si](O)(O)O6)O[Si](O)(O)O5
}}

'''Cristobalite''' ({{IPAc-en|k|r|ɪ|ˈ|s|t|oʊ|b|ə|l|aɪ|t}} {{respell|krist|OH|bə|lyte}}) is a [[mineral]] [[polymorphism (materials science)|polymorph]] of [[silicon dioxide|silica]] that is formed at very high temperatures. It has the same chemical formula as [[quartz]], [[silicon|Si]][[oxygen|O]]<sub>2</sub>, but a distinct crystal structure. Both quartz and cristobalite are polymorphs with all the members of the quartz group, which also include [[coesite]], [[tridymite]] and [[stishovite]]. It is named after Cerro San Cristóbal in [[Pachuca Municipality]], [[Hidalgo (state)|Hidalgo]], [[Mexico]].

It is used in dentistry as a component of [[alginate]] impression materials as well as for making models of teeth.<ref>{{Cite book |last=Anusavice, Kenneth J. |title=Phillips' science of dental materials |date=2013 |publisher=Elsevier/Saunders |isbn=978-1-4377-2418-9 |oclc=934359978}}</ref>