Trattnerite
| Trattnerite | |
|---|---|
| General and classification | |
| chemical formula | Fe 3+ 2 Mg 3 Si 12 O 30 |
|
Mineral class (and possibly department) |
Silicates and germanates - ring silicates |
|
System no. to Strunz and to Dana |
9.CM.05 ( 8th edition : VIII / E.22) 63.02.01a.17 |
| Similar minerals | Cordierite , Osumilite |
| Crystallographic Data | |
| Crystal system | hexagonal |
| Crystal class ; symbol | dihexagonal-dipyramidal; 6 / m 2 / m 2 / m |
| Space group | P 6 / mcc (No. 192) |
| Lattice parameters | a = 10.050 Å ; c = 14.338 Å |
| Formula units | Z = 2 |
| Frequent crystal faces | {001}, {100}, {101}, {111} |
| Twinning | - |
| Physical Properties | |
| Mohs hardness | not determined |
| Density (g / cm 3 ) | calculated: 2.68 |
| Cleavage | good after (001), bad after (100) |
| colour | dark blue to yellow green |
| Line color | White |
| transparency | transparent |
| shine | Glass gloss |
| Crystal optics | |
| Refractive indices |
n ω = 1.589 n ε = 1.586 |
| Birefringence | δ = 0.003 |
| Optical character | uniaxial negative |
| Pleochroism | strong: dark blue - yellow green |
The mineral trattnerite is a very rare ring silicate from the milarite group with the idealized chemical composition Fe 3+ 2 Mg 3 Si 12 O 30 . It crystallizes in the hexagonal crystal system and develops blue, platy to prismatic crystals a few millimeters in size.
Trattnerite is found in silicate-rich foreign rock inclusions in basalts . Besides its type locality , the hauyne - nephelinite -Steinbruch Stradner Kogel in Styria , Austria , Trattnerit has been detected only at another location of the same type, the basalt quarry Caspar on Ettringer Bellerberg in the Eifel , Germany .
Etymology and history
Trattnerite was discovered at the end of 1999 by Walter Trattner in the quarry on Stradner Kogel, where a thin basalt lava layer is being extracted. For determination, he gave his samples to the Landesmuseum Joanneum, where they were scientifically examined by the mineralogists around W. Postl. They characterized the new mineral as the □ -Fe 3+ analog of Merrihueit and named it after its discoverer Walter Trattner from Bad Waltersdorf in Styria, a passionate collector and specialist for the minerals of the Styrian volcanoes, who is another mineral, the Klöchit discovered the milarite group.
classification
In the outdated, but still partially common 8th edition of the mineral classification by Strunz Trattnerit belongs Almarudit , Armenit , Berezanskit , Brannockit , Chayesit , Darapiosit , Dusmatovit , Emeleusit , Faizievit , Merrihueit , Oftedalit , Osumilith , Osumilith- (Mg) , Poudretteit , Roedderite , Sogdianite , Sugilite and Yagiite to the general division of " Ring Silicates (Cyclosilicates)" in the " Milarit-Osumilith-Gruppe " with the system no. VIII / E.22 .
The 9th edition of Strunz's mineral systematics , which has been in force since 2001 and is used by the International Mineralogical Association (IMA), also classifies trattnerite in the "ring silicates" section. This is, however, further subdivided according to the structure of the rings, so that the mineral can be found in the sub-section "[Si 6 O 18 ] 12− -six double rings" according to its structure . Therein it is part of Agakhanovit- (Y) , Almarudit, Armenit, Berezanskit, Brannockit, Chayesit, Eifelit , Darapiosit, Dusmatovit, Friedrichbeckeit , Klöchit , Merrihueit, Milarit, Oftedalit, Osumilith, Osumilith- (Mg), Poudretteit, Roedderit, Shibkovit , Sogdianite, sugilite and yagiite to the " milarite group " with the system no. 9.CM.05 .
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the trattnerite to the class of "silicates and germanates", but there in the more finely subdivided division of "ring silicates: condensed rings". Here it is in the " Milarite Osumilith Group (Milarite Osumilith Subgroup) " with the system no. 63.02.01a can be found in the subsection “ Ring Silicates : Condensed, 6-membered Rings”.
Chemism
Trattnerite is the □ -Fe 3+ end link of a mixed crystal kingdom from Roedderite / Merrihueit via Chayesite to Trattnerite, which is responsible for the exchange reactions
- [B] Na + [T2] Mg 2+ = [B] □ + [T2] Fe 3+ (Roedderite - Chayesite)
- [C] K + [A] Mg 2+ = [C] □ + [A] Fe 3+ (chayesite - trattnerite)
underlie.
The measured composition from the type locality is [C] (Na 0.01 K 0.07 ) [A, T2] (Fe 3+ 1.99 Ti 0.01 Mg 2.46 Fe 2+ 0.30 Mn 2+ 0 , 08 Zn 0.05 Al 0.04 ) [T1] [Si 12 O 30 ], where the position in the crystal structure is indicated in square brackets.
Crystal structure
Trattnerite crystallizes in the hexagonal crystal system in the space group P 6 / mcc (space group no.192 ) with the lattice parameters a = 10.050 Å and c = 14.338 Å as well as two formula units per unit cell .
Trattnerite is isotypic to milarite , ie it crystallizes with the same structure as milarite. The 12-fold coordinated C position is empty, as is the 9-fold coordinated B position.
Iron is distributed equally between the 6-fold coordinated A position and the tetrahedral T2 position. Half of the A position contains trivalent cations (Fe 3+ ) and divalent cations (Mg, Fe 2+ ), the T2 position contains 1/3 Fe 3+ and 2/3 the divalent cations Mg, Fe 2+ .
The T1 position, which builds up the 6 double rings, only contains silicon (Si 4+ ).
Education and Locations
Trattnerite forms at high temperatures and low pressure under oxidizing conditions in silicon-rich and low -aluminum xenolites in basaltic magmas.
Trattnerite has only been documented at two sites worldwide (as of 2016).
At its type locality , the hauyne - nephelinite -Steinbruch the company Appel on the west side of the Stradner Kogels east of Wilhelmsdorf in Styria , Austria , to Trattnerit found in silicon-rich xenoliths from sanidine , plagioclase , quartz and rare green clinopyroxene . Deep blue trattnerite occurs together with tridymite , hematite , straw-yellow orthopyroxene and red-brown amphibole in small cavities of only a few millimeters in these foreign rock inclusions .
The second documented location is the Caspar quarry on the Bellerberg volcano near Ettringen , Mayen in the Eifel , Rhineland-Palatinate , Germany .
See also
Web links
Individual evidence
- ↑ a b c d e f g h i j k l m n o p q r s t u v w x Walter Postl, Franz Walter, Karl Ettinger, Christoph Hauzenberger, Hans-Peter Bojar: Trattnerite, (Fe, Mg) 2 (Mg, Fe) 3 [Si 12 O 30 ], a new mineral of the milarite group: mineral data and crystal structure . In: European Journal of Mineralogy . tape 16 , no. 2 , March 2004, p. 375-380 , doi : 10.1127 / 0935-1221 / 2004 / 0016-0375 ( rruff.info [PDF; 450 kB ; accessed on December 19, 2017]).
- ↑ Caspar Quarry, Bellerberg volcano, Ettringen, Mayen, Eifel, Rhineland-Palatinate, Germany
- ^ A b Walter Postl, Franz Walter, Karl Ettinger, Hans-Peter Bojar: About an almost alkali-free mineral of the Osumilite group from the nephelinite quarry on Stradner Kogel near Wilhelmsdorf, south of Bad Gleichenberg, Styria, Austria . In: Joannea Mineralogie . tape 1 , 2000, pp. 53–64 ( museum-joanneum.at [PDF; 571 kB ; accessed on December 19, 2017]).
- ↑ a b Stradner Kogel, Wilhelmsdorf, Bad Gleichenberg, Styria, Austria