Merrihueit
| Merrihueit | |
|---|---|
| General and classification | |
| other names |
IMA 1965-020 |
| chemical formula | (K, Na) 2 (Fe 2+ , Mg) 5 [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.05 |
| Similar minerals | Osumilith |
| 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 = 10.14 Å ; c = 14.22 Å |
| Formula units | Z = 2 |
| Physical Properties | |
| Mohs hardness | 6 to 7 |
| Density (g / cm 3 ) | calculated: 2.87 |
| Cleavage | is missing |
| Break ; Tenacity | not defined |
| colour | greenish blue |
| Line color | White |
| transparency | translucent |
| shine | Glass gloss |
| Crystal optics | |
| Refractive indices |
n ω = 1.570 n ε = 1.559 to 1.592 |
| Birefringence | δ = 0.011 |
| Optical character | uniaxial negative |
| Axis angle | 2V = measured: 5 to 10 ° |
| Pleochroism | colorless to greenish blue |
Merrihueit is a very rarely occurring mineral from the mineral class of " silicates and germanates ". It crystallizes in the hexagonal crystal system with the idealized chemical composition (K, Na) 2 (Fe 2+ , Mg) 5 [Si 12 O 30 ]. The cations potassium and sodium or iron and magnesium can represent each other in the crystal lattice ( substitution , diadochie), but are always in the same proportion to the silicate complex. Structurally, Merrihueit belongs to the ring silicates .
Merrihueit could only be found in the form of microcrystalline aggregates up to about 150 micrometers in size and as inclusions in enstatite . The mineral is translucent and greenish-blue in color with a glass-like sheen on the surfaces.
Etymology and history
Merrihueit was first discovered in mineral samples from the Mezö-Madaras meteorite , which fell in 1852 in Harghita County in the Romanian region of Transylvania . The mineral was described in 1965 by Robert T. Dodd Jr., W. Randall van Schmus and Ursula B. Marvin, who named it after the American geologist Craig M. Merrihue, who died recently.
classification
Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the Merrihueit belonged to the division of "ring silicates (cyclosilicates)", where it was used together with Almarudit , Armenit , Berezanskit , Brannockit , Chayesit , Darapiosit , Dusmatovit , Eifelit , Emeleusit , Faizievite , Milarite , Oftedalite , Osumilite , Osumilite- (Mg) , Poudretteit , Roedderite , Shibkovite , Sogdianite , Sugilite , Trattnerite , Yagiit and Yakovenchukit- (Y) the " Milarite-Osumilite Group " with the system no. VIII / E.22 .
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 classifies the Merrihueit in the "ring silicates" department. This is, however, further subdivided according to the structure of the rings, so that the mineral can be found according to its structure in the subsection "[Si 6 O 18 ] 12− -six double rings", where it is found together with almarudite, armenite, berezanskite, brannockite , Chayesit, Darapiosit, Dusmatovit, Eifelit, Friedrichbeckeit , Klöchit , Milarit, Oftedalit, Osumilith, Osumilith- (Mg), Poudretteit, Roedderit, Shibkovit, Sogdianit, Sugilith, Trattnerit and Yagiit the " Milaritgruppe " with the system-Nr. 9.CM.05 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the Merrihueit to the class of "silicates" and there in the department 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 ”.
Crystal structure
Merrihueit crystallizes hexagonally in the space group P 6 / mcc (space group no. 192) with the lattice parameters a = 10.14 Å and c = 14.22 Å as well as two formula units per unit cell .
properties
Merrihueit is pleochroitic , that is, depending on the direction from which the light falls through a crystal, it appears in a different color. At Merrihueit, the color varies between colorless and greenish-blue.
The index of refraction determined from the Meso-Maradas material is 1.559 to 1.592. The birefringence is low to moderate with δ = 0.011, which is expressed in the thin section by abnormal blue and violet interference colors .
Education and Locations
In Mesö-Maradas-Chondrit Merrihueit is a component of Chondrules and there substantially with clino-enstatite , fayalitischem olivine and nickel iron associated. It occurs there specifically in the form of inclusions in twinned clinoenstatite or clinobronzite, but its proportion is very small. Five thin sections and 10 grams of ground rock sample contained a total of just a few micrograms of the mineral.
Merrihueit of earthly origin is only known from three sites worldwide (as of 2014). The only known site in Germany so far is the "Caspar" quarry on Ettringer Bellerberg near Ettringen in the Rhineland-Palatinate Volcanic Eifel . Furthermore, Merrihueit has been detected in samples of volcanic rock with a basaltic composition. In a Miocene nepheline - basanite from Klöch in Styria zoned crystals of Merrihueit-Roedderit subgroup occurred, wherein the edge region of one of these crystals had the chemical composition of a Merrihueits.
The minerals of the Osumilith group apparently generally arise at high temperatures, whereby the Mg-rich minerals also form at high pressure, the Fe-rich minerals, to which Merrihueit belongs, at rather low pressure. It is therefore assumed that the Merrihueit fringe of the mineral grain from Klöch crystallized out during the ascent of the magma.
See also
literature
- Robert T. Dodd Jr., W. Randall van Schmus, Ursula B. Marvin: Merrihueite, A New Alkali-Ferromagnesian Silicate from the Mezö-Madaras Chondrite. In: Science. Volume 149, 1965, pp. 972-974. doi : 10.1126 / science.149.3687.972
- Karl Hans Wedepohl: Geochemistry . Collection Göschen . Walter de Gruyter, Berlin 1967, p. 35 (there with the spelling “Merrilmeit” ( Lapsus calami )).
Web links
Individual evidence
- ↑ a b c d Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties . 5th completely revised and supplemented edition. Weise, Munich 2008, ISBN 978-3-921656-70-9 .
- ↑ Webmineral - Merrihueite
- ^ A b c 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. 613 .
- ↑ a b Merrihueite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF kB )
- ↑ a b Mindat - Merrihueite
- ^ Robert T. Dodd Jr., W. Randall van Schmus, Ursula B. Marvin: Merrihueite, A New Alkali-Ferromagnesian Silicate from the Mezö-Madaras Chondrite. In: Science. Volume 149, 1965, pp. 972-974. doi : 10.1126 / science.149.3687.972
- ↑ Find location list for Merrihueit at the Mineralienatlas and at Mindat
- ↑ a b K. Ettinger, W. Postl, J. Taucher, F. Walter: Minerals of the Osumilith group (Roedderit / Merrihueit, Chayesit and Osumilith) from the Styrian-Burgenland volcanic area, Austria. In: Communications from the Department of Mineralogy at the Landesmuseum Joanneum. Issue 60/61, 1996, pp. 77–86 ( PDF 2.9 MB ( Memento of the original from January 30, 2016 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link accordingly Instructions and then remove this notice. )
