Lorenzenite
| Lorenzenite | |
|---|---|
 |
|
| General and classification | |
| other names |
Ramsayit |
| chemical formula | Na 2 Ti 2 [O 3 | Si 2 O 6 ] |
|
Mineral class (and possibly department) |
Silicates and Germanates |
|
System no. to Strunz and to Dana |
9.DB.10 ( 8th edition : VIII / F.03) 65.01.06.01 |
| Crystallographic Data | |
| Crystal system | orthorhombic |
| Crystal class ; symbol | orthorhombic dipyramida; 2 / m 2 / m 2 / m |
| Room group (no.) | Pnca (No. 60) |
| Lattice parameters | a = 14.49 Å ; b = 8.71 Å; c = 5.23 Å |
| Formula units | Z = 4 |
| Physical Properties | |
| Mohs hardness | 6th |
| Density (g / cm 3 ) | measured: 3.42 to 3.45; calculated: 3.44 |
| Cleavage | clearly after {010} |
| Break ; Tenacity | uneven; brittle |
| colour | light brown purple, light pink to mauve, brown to black |
| Line color | white to gray |
| transparency | transparent to opaque |
| shine | Glass gloss, diamond gloss, silk gloss or matt |
| Crystal optics | |
| Refractive indices |
n α = 1.910 to 1.950 n β = 2.010 to 2.040 n γ = 2.030 to 2.060 |
| Birefringence | δ = 0.120 |
| Optical character | biaxial negative |
| Other properties | |
| Special features | light yellow to pale green fluorescence under short-wave UV light |
Lorenzenite is a rarely occurring mineral from the mineral class of " silicates and germanates ". It crystallizes in the orthorhombic crystal system with the idealized chemical composition Na 2 Ti 2 [O 3 | Si 2 O 6 ], so chemically speaking it is a sodium - titanium- silicate, which structurally belongs to the chain silicates and ribbon silicates . A small proportion of niobium , iron , fluorine and zirconium can also be included as foreign admixtures .
In its pure form, lorenzenite is colorless and transparent. Due to multiple refraction due to lattice construction defects or polycrystalline training, it can also appear white and, due to foreign admixtures, take on a light brown-purple, light pink to mauve-like or brown to black color, whereby the transparency can decrease accordingly to the point of complete opacity.
Lorenzenite usually develops prismatic crystals with a thick tabular to needle-like habit , but also occurs in the form of fibrous to tomentose or lamellar mineral aggregates .
Etymology and history
Lorenzenite was first discovered near the former settlement Narsarsuaq (also Narssârssuk ) in northwest Greenland and described in 1897 by G. Flink, who named the mineral after the Danish mineralogist Johannes Theodor Lorenzen (1855-1884). The chemical analysis was carried out by R. Mauzelius.
1922 was an expedition under AE Fersman in nepheline - syenite on the Russian peninsula Kola a related mineral that first described by E. Kostyleva (published in 1923) and after the Finnish geologist Wilhelm Ramsay as Ramsayit was called. Kostyleva, however, already noticed the great similarity with lorenzenite in terms of chemical composition and crystal form when it was first described and assumed that the two minerals could be identical. With the help of further analyzes by Barth and Berman in 1930 and by Kraus and Mussgnuga in 1941, it was possible to correct the structural data of lorenzenite and thus prove that ramsayite and lorenzenite were practically identical. Only the composition differed slightly in that the lorenzenite sample analyzed by Mauzelius contained a significant proportion of zirconium (11.92% in the form of ZrO 2 ).
The renewed analysis of a very pure sample of the lorenzenite-type material by TG Sahama showed, however, that the zirconium content was negligibly small, just like with ramsayite. Even the foreign addition of niobium found in both samples was higher. Since, on the one hand, the original material analyzed by Mauzelius was no longer available and, on the other hand, the description by Flink lacked detailed information on the analytical method, Sahama could not clarify with absolute certainty whether Mauzelius' analysis was faulty or whether the zirconium content was simply a contamination of the sample depicted. In view of the amount of almost 12%, it is doubtful whether Mauzelius' sample could have been so impure. The possibility exists due to the association with the sodium zirconium silicate elpidite found at the type locality Narsaarsuk , but this mineral can be separated from the lorenzenite very easily.
In the German-speaking and western international-speaking areas, supported by the International Mineralogical Association (IMA), the name Lorenzenite (English Lorenzenite ) has now established itself , while in the Russian-speaking area the name Ramsayite is still widespread. However, the Finnish mineralogist Wilhelm Ramsay received an internationally recognized honor in 2004 for the newly discovered mineral Wilhelmramsayite .
classification
In the meantime outdated, but still in use 8th edition of the mineral classification by Strunz of lorenzenite belonged to the department of "chain silicates and band silicates (inosilicates)" where he collaborated with Balipholit , Ferrokarpholith , Kalikarpholith , carpholite , Kukisvumit , Lintisit , Magnesiokarpholith , Manganokukisvumit , Paravinogradovit , Vanadiokarpholith and vinogradovite the "Karpholithgruppe" with the system no. VIII / F.03 .
The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the IMA, also classifies lorenzenite in the category of "chain and band silicates (inosilicates)". However, this is further subdivided according to the structure of the chain formation, so that the mineral can be classified in the sub-section “Chain and ribbon silicates with 2-periodic single chains Si 2 O 6 ; with additional O, OH, H 2 O pyroxene-related minerals ”, where it is the only member of the unnamed group 9.DB.10 .
The systematics of minerals according to Dana , which is mainly used in the English-speaking area , also classifies the lorenzenite in the category of "chain silicate minerals". Here he is the namesake of the " Lorenzenite group " with the system no. 65.01.06 and the other members Kukisvumit, Lintisit, Manganokukisvumit and Punkaruaivit can be found in the subsection "Chain silicates: Simple unbranched chains, W = 1 with chains P = 2".
Crystal structure
Lorenzenite crystallizes orthorhombically in the space group Pnca (space group no. 60) with the lattice parameters a = 14.49 Å ; b = 8.71 Å and c = 5.23 Å and 4 formula units per unit cell .
properties
Under short-wave UV light , some Lorenzenites show a light yellow to pale green fluorescence , similar to that of neon-colored highlighters .
Education and Locations
Lorenzenite forms magmatic in alkaline syenites and syenitic pegmatites . As Begleitminerale occur among other Aegirin , apatite , Arfvedsonit , Astrophyllit , Elpidite , Eudialyt , ilmenite , Låvenit , loparite , microcline , nepheline , manganese Neptunit , Rinkit and titanite on.
As a rare mineral formation, lorenzenite is so far (as of 2013) only known from a few sites or in small numbers (according to mindat.org around 70 sites). In addition to its type locality Narsaarsuk, the mineral has so far only been found in Greenland at the “Gardiner complex ” near Kangerlussuaq and in the Ilimaussaq complex near Narsaq .
Well-known sites in Germany are the "Michelsberg" quarry on Katzenbuckel in Baden-Württemberg and the "Caspar" quarry on Ettringer Bellerberg near Ettringen in the North Rhine-Westphalian Eifel .
In Russia, due to the complex history of the mineral, the Kola peninsula became known as an area of discovery, with most of the Lorenzenite finds coming from the Chibinen and Lowosero Tundra massifs . Particularly worth mentioning is the Flora mountain in the Lowosero Tundra massif, where crystals of up to eight centimeters have been found.
Other locations are in Canada, Libya, Morocco, Norway, Spain, South Africa and Arkansas and New Mexico in the United States of America.
See also
literature
- Markku R. Sundberg, Martti Lehtinen, Raikko Kivekäs: Refinement of the crystal structure of ramsayite (lorenzenite) , in: American Mineralogist , Volume 72 (1987), pp. 173–177 ( PDF 519.5 kB )
- TG Sahama: Analysis of ramsayite and lorenzenite , in: American Mineralogist , Volume 32 (1947), pp. 59–63 ( PDF 303.4 kB )
- G. Flink: Undersøgelser af mineraler fra Julianehaab indsamlede - 27. Lorenzenite , in: On the minerals from Narsarsuk on the Firth of Tunugdliarfik in Southern Greenland , Meddelelser om Grønland , Volume 24, pp. 9–180 ( PDF 4.68 MB )
Web links
Individual evidence
- ↑ 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. 622 .
- ↑ Webmineral - Loren Zenite
- ↑ a b c d Lorenzenite , in: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 71 kB )
- ↑ a b Mindat - Lorenzenite
- ↑ a b TG Sahama: Analysis of ramsayite and lorenzenite , in: American Mineralogist , Volume 32 (1947), p. 61 ( PDF 303.4 kB ; p. 3)
- ↑ TG Sahama: Analysis of ramsayite and lorenzenite , in: American Mineralogist , Volume 32 (1947), p. 59 ( PDF 303.4 kB ; p. 1)
- ↑ TG Sahama: Analysis of ramsayite and lorenzenite , in: American Mineralogist , Volume 32 (1947), p. 63 ( PDF 303.4 kB ; p. 5)
- ↑ IMA / CNMNC List of Mineral Names (2009) - Lorenzenite (PDF 1.8 MB; p. 168)
- ↑ Mindat - Number of localities for Lorenzenite
- ↑ a b Locations for Lorenzenite near Mindat and the Mineralienatlas
- ↑ Petr Korbel, Milan Novák: Mineral Encyclopedia . Nebel Verlag GmbH, Eggolsheim 2002, ISBN 3-89555-076-0 , p. 237 ( Dörfler Natur ).