Jennite

• IMA 1965-021

The mineral Jennit is extremely rare in the chain silicate mineral from the class of " silicates and Germanates ". It crystallizes in the triclinic crystal system with the chemical composition CA9 [( OH) 4 | Si3O8OH ] 2 • 6H2O and developed along the b - axis elongated, flaky crystals of white color and stroke color.

Special Features

At a temperature about 90 ° C Jennit pass upon delivery of crystal water in meta Jennit with monoclinic structure.

Etymology and history

Was first discovered by Colonel Clarence Marvin Jenni Jennit (1896-1973) in the Crestmore quarry in Riverside County in the U.S. state of California, and described in 1966 by AB Carpenter, R. A. Calmers, JA Gard, K. Speakman, HFW Taylor, who named the mineral after its first discoverer.

In contrast to the first chemical analysis by Carpenter Jennit does not contain appreciable amounts of sodium, as some later samples tested showed.

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz the Jennit belonged to the mineral class of " silicates and Germanates " and then to the Department of " chain silicates and phyllosilicates ( inosilicates ) " where he, along with Bustamite, Cascandit, Denisovite Ferrobustamit, Foshagite, Pectolite, Serandit, Vistepit, wollastonite 1A and wollastonite -2M formed a distinct group.

The 9th edition valid since 2001 and of the International Mineralogical Association (IMA ) used the Strunz'schen Mineral classification assigns the Jennit also in the class of " silicates and Germanates " and there in the department of " chains and chain silicates ( inosilicates ) " one. This division, however, is further subdivided according to the type of chain formation, so that the mineral is " with 3- periodic single and multiple chains chains and chain silicates " to find according to its construction in the subdivision where it is the only member of the unnamed group 9 DG.20 forms.

The mainly common in English-speaking classification of minerals according to Dana assigns the Jennit in the class of " silicates and Germanates " and then in the Department of: a " group silicates Si2O7 Groups and O, OH, F, and H2O". Here he is with Baghdadit, Burpalit, cuspidine Lavenit, Wohlerit, Niocalit, Hiortdahlit, rosenbuschite, Hainite, Janhaugit, Komarovit, Natrokomarovit, Suolunit, Mongolit, Kristiansenit, Kochit and Marianoit in the " cuspidine - Wohlerit group " with the system no. ": With cations and / or Si2O7 Groups and O, OH, F, and H2O > Coordination Group silicates " to find 56.02.04 within the subdivision.

Education and Locations

Jennit formed at a late stage of crystallization as a partial filling of cavities and veins in contact metamorphic rocks such as Skarn. Accompanying minerals include Afwillit, calcite, Oyelit, Scawtite, spurrite and tobermorite.

As a rare mineral Jennit has so far been demonstrated only in a few localities, so far (as of 2011) are about 15 known localities. Apart from its type locality Crestmore in California in the United States, the mineral, among others still found in Boisséjour in the French region of Auvergne, on Zeilberg in Bavaria and on Ettringer Bellerberg at Ettringen in North Rhine -Westphalia in Germany, in the Hatrurim Basin of the Israeli Negev Desert, in the Italian towns Montalto di Castro and Spoleto, on the Japanese island of Honshu, in the municipality Zitácuaro in the Mexican state of Michoacán, on Lakargi in the Russian republic of Kabardino -Balkaria, in the Slovak community Vechec, in the case Hotazel ​​in the South African Kalahari located Wessels Mine, as well as at Fort Portal, Uganda.

Crystal structure

Jennit crystallizes in the triclinic space group P1 ( Raumgruppen-Nr. 2) with the lattice parameters a = 10.58 Å; b = 7.27 Å; c = 10.83 Å; α = 99.6 °; β = 97.6 ° and γ = 110.2 ° and one formula unit per unit cell.