Marialith

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Marialith
Marialite-169082.jpg
A 2.3 cm long, yellowish marialite crystal from the Morogoro marble deposit , Uluguru Mountains, Tanzania
General and classification
other names

Mizzonite from Pianura

chemical formula Na 4 [Cl | Al 3 Si 9 O 24 ]
Mineral class
(and possibly department) 		Silicates and Germanates
System no. to Strunz
and to Dana 		9.FB.15 ( 8th edition : VIII / J.13)
76.03.01.01
Crystallographic Data
Crystal system tetragonal
Crystal class ; symbol tetragonal-dipyramidal 4 / m
Room group (no.) I 4 / m (No. 87)
Lattice parameters a  = 12.05  Å ; c  = 7.57 Å
Formula units Z  = 2
Physical Properties
Mohs hardness 5.5 to 6
Density (g / cm 3 ) measured: 2.50 to 2.62; calculated: [2.54]
Cleavage clearly after {100}, {110}
Break ; Tenacity uneven to scalloped
colour colorless, white, gray, pink to violet, blue, yellow, brown, orange-brown
Line color White
transparency transparent to opaque
shine Glass gloss, pearlescent
Crystal optics
Refractive indices n ω  = 1.539 to 1.550
n ε  = 1.532 to 1.541
Birefringence δ = 0.007 to 0.009
Optical character uniaxial negative
Other properties
Special features fluorescence

Marialite is a rarely occurring mineral from the mineral class of " silicates and germanates ". It crystallizes in the tetragonal crystal system with the composition Na 4 [Cl | Al 3 Si 9 O 24 ], and is thus chemically seen a sodium - Gerüstalumosilikat with chlorine as an additional anion .

Marialith mostly develops prismatic crystals with flat, pyramidal ends with shiny glass surfaces, but also columnar or granular to massive mineral aggregates . In its pure form, the mineral is colorless and transparent. However, due to multiple light refraction due to lattice construction defects or multicrystalline formation, it can also appear white and, due to foreign admixtures, take on a gray, pink to violet, blue, yellow, brown or orange-brown color. However, his line color is always white.

Special properties

Under UV light , some marialiths show orange to light yellow or red fluorescence .

Etymology and history

Marialith was first discovered near Pianura in the Phlegraean Fields in the Italian province of Naples .

The name Marialith von Ryllo was originally given to a white Berzellin by Albano. However, Gerhard vom Rath was able to prove in 1866 that Berzelin was identical to the already known Haüyn . Berzelin as a separate mineral had to be deleted and accordingly the variety name Marialith lost its meaning.

Vom Rath proposed the name Marialith, which had become free, as a name for a mineral newly discovered by Pianura, which he himself temporarily referred to as Pianura mizzonite due to its similarity to mizzonite .

classification

In the meantime outdated, but still in use 8th edition of the mineral classification by Strunz of Marialite belonged to the mineral class of "silicates and Germanates" and then to the Department of " framework silicates where he (tectosilicates)" along with Kalborsit , Mejonit , Sarkolith and Silvialith independent " Scapolite series" with the system no. VIII / J.13 formed.

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), also assigns the marialite to the class of “silicates and germanates”, but in the newly defined section of “tectosilicates” without zeolitic H 2 O “. This section is further subdivided according to the possible presence of further anions, so that the mineral, according to its composition, can be found in the subdivision of "tectosilicates (tectosilicates) with additional anions", where it only forms the "scapolite group" together with mejonite and silvialite with the system no. 9.FB.15 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the marialite to the class of "silicates and Germanates" and there in the department of "framework silicates: Al-Si lattice". Here he is together with Mejonit and Silvialith in the "Scapolite group" with the system no. 76.03.01 to be found in the subdivision “ 76.03 Framework silicates: Al-Si grids with other Be / Al / Si grids ”.

Education and Locations

Marialith is formed in rocks that have been shaped by regional metamorphosis, such as marble , calcareous gneisses , granulites and green slate . It can also be found in some skarns and pegmatites as well as in pneumatolytically or hydrothermally converted igneous rocks. Accompanying minerals include various plagioclases , garnets , pyroxenes , amphiboles , apatites, as well as titanite and zircon .

As a rare mineral formation, Marialith could so far (status: 2011) only be proven at a few sites. Around 95 sites are known to be known. In addition to its type locality Pianura, the mineral occurred at Soccavo in the Phlegraean Fields, at Ercolano and Sant'Anastasia near Monte Somma , on Procida and at Lavorate (Salerno) in Campania; near Val di Fà in Valcamonica in Lombardy and in the “Cape Arco Mine” near Porto Azzurro on Elba.

In Austria, the mineral was found in a spodumene trial mining on the ridge of fire in Carinthia (see also Mining in Carinthia ).

Other sites are in Australia, Brazil, Chile, China, France, Japan, Canada, Nepal, Norway, Russia, Sweden, Spain, South Africa, Tanzania, the Czech Republic, the United Kingdom (Great Britain) and the United States (USA).

Crystal structure

Marialith crystallizes tetragonally in the space group I 4 / m (space group no. 87) with the lattice parameters a  = 12.05  Å and c  = 7.57 Å as well as 2 formula units per unit cell .

See also

literature

Web links

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

Individual evidence

  1. ^ A b Gerhard vom Rath (1866): Mineralogical-geognostic fragments from Italy. In: Journal of the German Geological Society. Volume 18, p. 637. ( PDF 5.9 MB )
  2. ↑ 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 , p.  700 .
  3. ↑ Webmineral - Maria Lite
  4. ↑ a b c d John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols: Marialite. In: Handbook of Mineralogy, Mineralogical Society of America. 2001. ( PDF 73.5 kB )
  5. ↑ a b c Mindat - Marialite
  6. ^ Gerhard vom Rath (1866): Mineralogical-geognostic fragments from Italy. In: Journal of the German Geological Society. Volume 18, p. 549. ( PDF 5.9 MB )
  7. ↑ Mindat - Number of localities for Marialith