# Datolite

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Nesosilicate mineral

Datolite Datolite on sphalerite from San Luis Potosí, Mexico (size: 6.2 x 5.3 x 2.8 cm) General Category Nesosilicate Formula CaBSiO4(OH) IMA symbol Dat[1] Strunz classification 9.AJ.20 Crystal system Monoclinic Crystal class Prismatic (2/m) (same H-M symbol) Space group P21/c Unit cell a = 9.62, b = 7.6 c = 4.84 [Å]; β = 90.15°; Z = 4 Identification Color Colorless or white; may be grayish, yellow, green, pale green, red, pink, etc. Crystal habit Crystal prismatic, short to tabular; Botryoidal or globular with columnar structure; granular to compact; cryptocrystalline Cleavage None Fracture Conchoidal to uneven Tenacity Brittle Mohs scale hardness 5 to 5.5 Luster Vitreous, rarely subresinous on fracture surface Diaphaneity Transparent to translucent, rarely opaque Specific gravity 2.96 – 3.00 Optical properties Biaxial (-) Refractive index nα = 1.626 nβ = 1.653 - 1.654 nγ = 1.670 Birefringence δ = 0.044 2V angle Measured: 74° Dispersion r > v; weak Ultraviolet fluorescence Fluoresces blue under SW UV References [2][3][4]

**Datolite** is a [calcium](/source/Calcium) [boron](/source/Boron) [hydroxide](/source/Hydroxide) [nesosilicate](/source/Silicate_minerals), [Ca](/source/Calcium)[B](/source/Boron)[Si](/source/Silicon)[O](/source/Oxygen)4(O[H](/source/Hydrogen)). It was first observed by [Jens Esmark](/source/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.[5]

Datolite crystallizes in the [monoclinic](/source/Monoclinic) system forming prismatic [crystals](/source/Crystal) and nodular masses. The luster is vitreous and may be brown, yellow, light green or colorless. The [Mohs hardness](/source/Mohs_hardness) is 5.5 and the [specific gravity](/source/Specific_gravity) is 2.8 - 3.0.

Polished datolite nodule from the [Quincy Mine](/source/Quincy_Mine) of Michigan’s Copper Country (size: 4.1 x 3.3 x 1.7 cm)

The [type localities](/source/Type_locality_(geology)) are in the [diabases](/source/Diabase) of the [Connecticut River](/source/Connecticut_River) valley and [Arendal](/source/Arendal), [Aust-Agder](/source/Aust-Agder), [Norway](/source/Norway). Associated minerals include [prehnite](/source/Prehnite), [danburite](/source/Danburite), [babingtonite](/source/Babingtonite), [epidote](/source/Epidote), native [copper](/source/Copper), [calcite](/source/Calcite), [quartz](/source/Quartz) and [zeolites](/source/Zeolite). It is common in the copper deposits of the [Lake Superior](/source/Lake_Superior) region of [Michigan](/source/Michigan). It occurs as a secondary mineral in [mafic](/source/Mafic) [igneous rocks](/source/Igneous_rocks) often filling vesicles along with zeolites in [basalt](/source/Basalt). Unlike most localities throughout the world, the occurrence of datolite in the [Lake Superior](/source/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](/source/Botryoidal) form of datolite.

## References

1. **[^](#cite_ref-1)** Warr, L.N. (2021). ["IMA–CNMNC approved mineral symbols"](https://doi.org/10.1180%2Fmgm.2021.43). *Mineralogical Magazine*. **85** (3): 291–320. [Bibcode](/source/Bibcode_(identifier)):[2021MinM...85..291W](https://ui.adsabs.harvard.edu/abs/2021MinM...85..291W). [doi](/source/Doi_(identifier)):[10.1180/mgm.2021.43](https://doi.org/10.1180%2Fmgm.2021.43). [S2CID](/source/S2CID_(identifier)) [235729616](https://api.semanticscholar.org/CorpusID:235729616).

1. **[^](#cite_ref-HBM_2-0)** [Handbook of Mineralogy](http://rruff.geo.arizona.edu/doclib/hom/datolite.pdf)

1. **[^](#cite_ref-Mindat_3-0)** [Mindat](http://www.mindat.org/min-1340.html)

1. **[^](#cite_ref-Webmin_4-0)** [Webmineral](http://webmineral.com/data/Datolite.shtml)

1. **[^](#cite_ref-5)** One or more of the preceding sentences incorporates text from a publication now in the [public domain](/source/Public_domain): [Chisholm, Hugh](/source/Hugh_Chisholm), ed. (1911). "[Datolite](https://en.wikisource.org/wiki/1911_Encyclop%C3%A6dia_Britannica/Datolite)". *[Encyclopædia Britannica](/source/Encyclop%C3%A6dia_Britannica_Eleventh_Edition)*. Vol. 7 (11th ed.). Cambridge University Press. p. 846.

## External links

Wikimedia Commons has media related to [Datolite](https://commons.wikimedia.org/wiki/Category:Datolite).

- [Mineral galleries](https://web.archive.org/web/20050912110432/http://mineral.galleries.com/minerals/silicate/datolite/datolite.htm)

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