Mesolite

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Mesolite
Mesolite - Poona, India.jpg
Mesolite from Poona, India
General and classification
chemical formula Na 2 Ca 2 [Al 6 Si 9 O 30 ] • 8H 2 O
Mineral class
(and possibly department) 		Framework silicates (tectosilicates)
System no. to Strunz
and to Dana 		9.GA.05 ( 8th edition : VIII / J.21)
77.01.05.04
Similar minerals Natrolite , Skolezite
Crystallographic Data
Crystal system orthorhombic
Crystal class ; symbol orthorhombic-pyramidal; mm 2
Space group Fdd 2 (No. 43)Template: room group / 43
Lattice parameters a  = 18.41  Å ; b  = 56.65 Å; c  = 6.55 Å
Formula units Z  = 8
Physical Properties
Mohs hardness 5
Density (g / cm 3 ) 2.2 to 2.4
Cleavage completely according to {101} and {001}
Break ; Tenacity uneven, mussel-like
colour colorless, white, pale yellow
Line color White
transparency transparent to translucent
shine Glass gloss, silk gloss
Crystal optics
Refractive index n  = 1.505
Birefringence δ = biaxial

Mesolite is a frequently occurring mineral from the mineral class of silicates , more precisely a framework silicate from the group of fiber zeolites . It crystallizes in the orthorhombic crystal system with the chemical composition Na 2 Ca 2 [Al 6 Si 9 O 30 ] · 8H 2 O and develops mainly long, needle-like to hair-like crystals in radially arranged aggregates or coarse, porcelain-like masses that are mostly colorless or white .

From a mineralogical point of view, mesolite is an intermediate link in a continuous series of chemical mixtures , which is characterized by the exchange of calcium and water instead of sodium . The sodium-rich end member of the series (with the same crystal structure ) is natrolite (Na 2 [Al 2 Si 3 O 10 ] · 2H 2 O), the calcium-rich end member is scolecite (Ca [Al 2 Si 3 O 10 ] · 3H 2 O), while mesolite is of intermediate composition with a significant proportion of sodium and calcium.

Etymology and history

The name mesolite was first used in 1813 by the German scholars Adolph Ferdinand Gehlen and Johann Nepomuk Fuchs for a variety of "mesotype" , but without specifying the location. The definition of the name, which is still used today as an intermediate link between natrolite and skolezite , was introduced three years later, in 1816, by JN Fuchs.

classification

In the meantime outdated, but still in use 8th edition of the mineral classification by Strunz of Mesolith belonged to the mineral class of "silicates and Germanates" and then to the Department of " framework silicates (tectosilicates)" where he collaborated with Gonnardite , natrolite , Paranatrolith , Skolezit , Thomsonite (Ca) and Thomsonite (Sr) formed the independent " zeolite group , subgroup fiber zeolites".

Since 2001, fixed by the International Mineralogical Association used (IMA) 9th edition of Strunz'schen systematic mineral also assigns the Mesolith in the class of "silicates and Germanates" and then in the Department of the " framework silicates (tectosilicates) with zeolitic H 2 O; Family of zeolites ”. However, this section is further subdivided according to the structure of the rings, so that the mineral can be found according to its structure in the sub-section "Zeolites with four-ring chains connected via a fifth Si", where it is only found together with gonnardite, natrolite, paranatrolite and Skolezit forms the unnamed group 9.GA.05 .

The systematics of minerals according to Dana also assigns the mesolite to the class of "silicates and germanates" and there into the department of "framework silicates: zeolite group". Here it is together with natrolite, tetranatrolite , paranatrolite, skolezite, edingtonite , gonnardite, cowlesite , thomsonite-Ca, thomsonite-Sr and nabesite in the group "natrolite and related species" with the system no. 77.01.05 to be found within the sub-section of " Real Zeolites ".

Crystal structure

Mesolite crystallizes orthorhombically in the space group Fdd 2 (space group no. 43) with the lattice parameters a  = 18.41  Å ; b  = 56.65 Å and c  = 6.55 Å and 8 formula units per unit cell . Template: room group / 43

Education and Locations

Needle-like mesolite on analcime crystals from the Bear Creek Pit (Whipple Pit), Drain, Douglas County, Oregon, USA (4.6 cm × 2.6 cm)

Like the related minerals scolezite and natrolite, mesolite is a widespread decomposition product of basalt and occurs in it together with other zeolites and apophyllite as a hydrothermal formation in drusen . Also in some igneous and metamorphic rocks , scolezite occurs as a fissure mineral . Mesolite is formed during the low-grade metamorphosis in the zeolite facies.

Well-known sites are among others on the Faroe Islands , Iceland , Isle of Skye and India ( Maharashtra ).

See also

Web links

Commons : Mesolite  - collection of images, videos and audio files

Individual evidence

  1. ↑ a b c d e Hugo Strunz , Ernest H. Nickel: Strunz Mineralogical Tables . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X .
  2. ^ AF Gehlen, JN Fuchs: Ueber Werner's Zeolith, Haüy's Mesotype and Stilbite. In: (Schweigger's) Journal for Chemistry and Physics Volume 8, 1813, pp. 353-366. ( limited preview in Google Book search)
  3. ^ DC Coombs, A. Alberti, T. Armbruster, G. Artioli, C. Colella, E. Galli, JD Grice, F. Liebau, JA Mandarino, H. Minato, EH Nickel, E. Passaglia, DR Peacor, S. Quartieri, R. Rinaldi, M. Ross, RA Sheppard, E. Tillmanns, G. Vezzalini: Recommended nomenclature for zeolite minerals: report of the subcommittee on zeolites of the International Mineralogical Association, Commission on New Minerals and Mineral Names. In: Mineralogical Magazine. Volume 62, 1998, pp. 533-571.
  4. ↑ JN Fuchs: About the zeolites. In: (Schweigger's) Journal for Chemistry and Physics Volume 18, 1816, pp. 1-29. ( limited preview in Google Book search)
  5. ^ Friedrich Klockmann : Klockmanns textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke , Stuttgart 1978, ISBN 3-432-82986-8 , pp.  791 (first edition: 1891).