Hellenica World

Jennite

Jennite is a calcium silicate hydrate (CSH) of general chemical formula:

Ca9Si6O18(OH)6 · 8 H2O

Jennite occurs in hydrated cement paste and can be found in nature in particular conditions, e.g., as alteration mineral in metamorphosed limestone and skarn.

A first specimen of jennite found in 1966 at the Crestmore quarries (Crestmore, Riverside County, California, USA) was analysed and identified as a new mineral by Carpenter et al. (1966). They named it in honour of its discoverer: Clarence Marvin Jenni (1896-1973) director of the Geological Museum at the University of Missouri.

In contrast to the first analysis made by Carpenter et al. (1966), jennite does not contain appreciable amount of sodium as confirmed by Gard et al. (1977) when they reexamined the specimen found at Crestmore.

The structure of jennite determined by Bonaccorsi et al. (2004) is made of three distinct modules: ribbons of edge-sharing calcium octahedra, silicate chains of wollastonite-type running along b axis, and additional calcium octahedra on inversion centers. The hydroxyl groups are bonded to three calcium cations while no SiOH groups are observed.

Jennite transforms to metajennite at 70 – 90 °C by losing four water molecules.

External links

* Jennite on Webmineral
* Jennite on Mindat
* Jennite in the American Mineralogist Crystal Structure Database


References

* Abdul-Jaber, Q.H.; Khoury, H. (1998), "Unusual mineralisation in the Maqarin Area (North Jordan) and the occurrence of some rare minerals in the marbles and the weathered rocks", Neues Jahrb. Geol. Paläontol. Abh. 208: 603–629

* Bonaccorsi, E.; Merlino, S.; Taylor, H.F.W. (2004), "The crystal structure of jennite, Ca9Si6O18(OH)6 · 8 H2O, Locality: Fuka, Japan", Cement and Concrete Research 34: 1481–1488, doi:10.1016/j.cemconres.2003.12.033, http://rruff.geo.arizona.edu/AMS/result.php?mineral=Jennite, retrieved 2009-02-04

* Carpenter, A.B.; Chalmers, R.A.; Gard, J.A.; Speakman, K.; Taylor, H.F.W. (1966), "Jennite, a new mineral", American Mineralogist 51: 56–74, http://www.minsocam.org/ammin/AM62/AM62_365.pdf, retrieved 2009-02-04

* Chen, Jeffrey J.; Jeffrey J. Thomas, Hal F.W. Taylor, Hamlin M. Jennings (2004), "Solubility and structure of calcium silicate hydrate", Cement and Concrete Research 34 (9): 1499–1519, doi:10.1016/j.cemconres.2004.04.034, ISSN 0008-8846, http://www.sciencedirect.com/science/article/B6TWG-4CNH51T-1/2/7466036d6266db6640c8bcbcbee3bc9f, retrieved 2009-02-04

* Eakle, Arthur S. (1927), "Famous mineral localities: Crestmore, Riverside County, California", American Mineralogist 12: 319–321, http://www.minsocam.org/MSA/collectors_corner/arc/crestmoreca1.htm, retrieved 2009-11-01

* Gard, J.A.; Taylor, H.F.W.; Cliff, G.; Lorimer, G.W. (1977), "A reexamination of jennite", American Mineralogist 62: 365–368, http://www.minsocam.org/ammin/AM62/AM62_365.pdf, retrieved 2009-02-04

* Naomichi, Hara (2000), "Formation of jennite and tobermorite from amorphous silica.", J. Soc. Inorg. Mater. Japan 7 (285): 133–142, ISSN 1345-3769, http://sciencelinks.jp/j-east/article/200011/000020001100A0298196.php, retrieved 2009-02-04

* Merlino, S.; Bonaccorsi E., Armbruster T. (2001), "The real structure of tobermorite 11A: normal and anomalous forms, OD character and polytypic modifications (Note: MDO2 - synchrotron radiation source. Locality: Bascenov, Urals, Russia)", European Journal of Mineralogy 13: 577–590

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