View source for Datolite

{{Short description|Nesosilicate mineral}}
{{Infobox mineral
| name = Datolite
| category = [[Nesosilicate]]
| image = Datolite-rom25c.jpg
| imagesize   = 260px
| caption = Datolite on sphalerite from San Luis Potosí, Mexico (size: 6.2 x 5.3 x 2.8 cm)
| formula     = CaBSiO<sub>4</sub>(OH)
| IMAsymbol   = Dat<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.AJ.20
| dana        = 
| system      = [[Monoclinic]]
| class       = Prismatic (2/m) <br/><small>(same [[H-M symbol]])</small>
| symmetry    = ''P''2<sub>1</sub>/c
| unit cell   = a = 9.62, b = 7.6 <br/>c = 4.84&nbsp;[Å]; β = 90.15°; Z&nbsp;=&nbsp;4
| color       = Colorless or white; may be grayish, yellow, green, pale green, red, pink, etc.
| colour      = 
| habit       = Crystal prismatic, short to tabular; Botryoidal or globular with columnar structure; granular to compact; cryptocrystalline
| twinning    = 
| cleavage    = None
| fracture    = Conchoidal to uneven
| tenacity    = Brittle
| mohs        = 5 to 5.5
| luster      = Vitreous, rarely subresinous on fracture surface
| streak      = 
| diaphaneity = Transparent to translucent, rarely opaque
| gravity     = 2.96 – 3.00
| density     = 
| polish      = 
| opticalprop = Biaxial (-)
| refractive  = n<sub>α</sub> = 1.626 n<sub>β</sub> = 1.653 - 1.654 n<sub>γ</sub> = 1.670
| birefringence = δ = 0.044
| pleochroism = 
| 2V          = Measured: 74°
| dispersion  = r > v; weak
| extinction  = 
| length fast/slow =
| fluorescence = Fluoresces blue under SW UV
| absorption  = 
| melt        = 
| fusibility  = 
| diagnostic  = 
| solubility  = 
| impurities  = 
| alteration  = 
| other       = 
| references = <ref name=HBM>[http://rruff.geo.arizona.edu/doclib/hom/datolite.pdf Handbook of Mineralogy]</ref><ref name=Mindat>[http://www.mindat.org/min-1340.html Mindat]</ref><ref name=Webmin>[http://webmineral.com/data/Datolite.shtml Webmineral]</ref>
}}
'''Datolite''' is a [[calcium]] [[boron]] [[hydroxide]] [[Silicate minerals|nesosilicate]], [[calcium|Ca]][[boron|B]][[silicon|Si]][[oxygen|O]]<sub>4</sub>(O[[hydrogen|H]]). It was first observed by [[Jens Esmark]] in 1806, and named by him from δατεῖσθαι, "to divide," and  λίθος, "stone," in allusion to the granular structure
of the massive mineral.<ref>{{EB1911|inline=1|wstitle=Datolite|volume=7|page=846}}</ref>

Datolite crystallizes in the [[monoclinic]] system forming prismatic [[crystal]]s and nodular masses. The luster is vitreous and may be brown, yellow, light green or colorless. The [[Mohs hardness]] is 5.5 and the [[specific gravity]] is 2.8 - 3.0. 
[[File:Datolite-132458.jpg|thumb|left|Polished datolite nodule from the [[Quincy Mine]] of Michigan’s Copper Country (size: 4.1 x 3.3 x 1.7 cm)]]
The [[Type locality (geology)|type localities]] are in the [[diabase]]s of the [[Connecticut River]] valley and [[Arendal]], [[Aust-Agder]], [[Norway]]. Associated minerals include [[prehnite]], [[danburite]], [[babingtonite]], [[epidote]], native [[copper]], [[calcite]], [[quartz]] and [[zeolite]]s. It is common in the copper deposits of the [[Lake Superior]] region of [[Michigan]]. It occurs as a secondary mineral in [[mafic]] [[igneous rocks]] often filling vesicles along with zeolites in [[basalt]]. Unlike most localities throughout the world, the occurrence of datolite in the [[Lake Superior]] region is usually fine grained in texture and possesses colored banding. Much of the coloration is due to the inclusion of copper or associated minerals in progressive stages of hydrothermal precipitation.

''Botryolite'' is a [[botryoidal]] form of datolite.

==References==
{{reflist}}

==External links==
{{commons category|Datolite}}
*[https://web.archive.org/web/20050912110432/http://mineral.galleries.com/minerals/silicate/datolite/datolite.htm Mineral galleries]

[[Category:Calcium minerals]]
[[Category:Nesosilicates]]
[[Category:Gemstones]]
[[Category:Monoclinic minerals]]
[[Category:Minerals in space group 14]]
[[Category:Luminescent minerals]]