Umbit
| Umbit | |
|---|---|
| General and classification | |
| other names |
IMA 1982-006 |
| chemical formula | K 2 Zr [Si 3 O 9 ] • H 2 O |
|
Mineral class (and possibly department) |
Silicates and Germanates - chain silicates and band silicates (inosilicates) |
|
System no. to Strunz and to Dana |
9.DG.25 ( 8th edition : VIII / F.20) 59.02.01.01 |
| Crystallographic Data | |
| Crystal system | orthorhombic |
| Crystal class ; symbol | orthorhombic-disphenoidic; 222 |
| Space group | P 2 1 2 1 2 1 (No. 19) |
| Lattice parameters | a = 10.21 Å ; b = 13.24 Å; c = 7.17 Å |
| Formula units | Z = 4 |
| Frequent crystal faces | {010}, {101}, {110}, {001} |
| Physical Properties | |
| Mohs hardness | 4.5 |
| Density (g / cm 3 ) | measured and calculated: 2.79 |
| Cleavage | perfect and mica-like after {010}; imperfect after {100} |
| colour | colorless, yellowish white |
| Line color | White |
| transparency | transparent to translucent |
| shine | Glass gloss |
| Crystal optics | |
| Refractive indices |
n α = 1.596 n β = 1.619 n γ = 1.630 |
| Birefringence | δ = 0.034 |
| Optical character | biaxial negative |
| Axis angle | 2V = 80 ° (measured); 68 ° (calculated) |
| Other properties | |
| Chemical behavior | soluble in 10% hydrochloric acid |
| Special features | slightly yellowish fluorescence |
Umbit is a very rarely occurring mineral from the mineral class of "silicates and germanates" with the chemical composition K 2 Zr [Si 3 O 9 ] · H 2 O and is therefore chemically a water-containing potassium - zirconium - silicate .
Umbit crystallizes in the orthorhombic crystal system , but has so far only been discovered in the form of millimeter-sized, predominantly tabular crystals that are flattened perpendicular to the b-axis and have a glass-like sheen on the surface . In its pure form, umbit is colorless and transparent. However, due to multiple refraction due to lattice construction defects or polycrystalline formation, it can also be translucent white and take on a yellowish color due to foreign admixtures.
Etymology and history
Umbit was first discovered in a drill core from the Vuonnemiok river valley in the eastern part of the Chibinen and about 20 km west of Lake Umbosero (Lake Umba) on the Russian Kola Peninsula . The mineral was described in 1983 by AP Khomyakov, AA Voronkov, Yu. S. Kobyashev and LI Polezhaeva, who named it to the lake located near the type locality .
Type material of the mineral is found in the Geological Museum of the Science Center of the Russian Academy of Sciences in Apatity on Kola; in the Mineralogical Museum of the University of Saint Petersburg under catalog no. 17072 ; at the Mining Institute in Saint Petersburg under catalog no. 1631/1 ; in the Fersman Museum in Moscow under catalog no. 82758 and in the Natural History Museum in London under catalog no. 1994.35 kept.
classification
Already in the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , the umbit belonged to the mineral class of "silicates and germanates" and there to the department of "chain silicates and band silicates (inosilicates)", where together with paraumbit it belonged to the unnamed group VIII /F.20 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 classifies the umbit under the category of “chain and band silicates”. However, this is further subdivided according to the structure of the chains, so that the mineral can be found according to its structure in the sub-section "Chain and band silicates with 3-periodic single and multiple chains", where it is also group 9, together with Paraumbit . DG.25 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the umbit to the class of "silicates and germanates", but there in the department of "ring silicates: triple rings". Here he is together with Paraumbit and Kostylevit in the group "Umbit and allied species" with the system no. 59.02.01 to be found in the subsection " Ring Silicates: Water-Containing Triple Rings ".
Crystal structure
Umbit crystallizes orthorhombically in the space group P 2 1 2 1 2 1 (space group no. 19) with the lattice parameters a = 10.21 Å ; b = 13.24 Å; c = 7.17 Å and 4 formula units per unit cell .
properties
Under UV light , some umbites show a slightly yellowish fluorescence , similar to that of neon-colored highlighters .
Umbit is easily soluble in cold 10% hydrochloric acid .
Modifications and varieties
The compound K 2 Zr [Si 3 O 9 ] · H 2 O is dimorphic and, in addition to the orthorhombically crystallizing umbit, also occurs as a monoclinic crystallizing Kostylevite .
Education and Locations
Umbit forms in pegmatitic veins that have permeated nepheline - syenite . There it is found in the interstices of coarsely crystalline potassium feldspar in paragenesis with aegirine , arctite , converted eudialyte , Kostylevite, natrolite , pectolite and other accompanying minerals.
In addition to its type locality in the Vuonnemiok river valley, the mineral could also be found in other places in the Chibinen such as the Koaschwa mine on the mountain of the same name, in a wadeit deposit on Eweslogchorr (Eveslogchorr) , Kukiswumtschorr (Kukisvumchorr) , Rischorr and Yukspor . In addition, umbit has so far only been discovered on the Alluaiw in the Lowosero Tundra massif (as of 2017).
See also
literature
- AP Khomyakov, AA Voronkov, Yu. S. Kobyashev, LI Polezhaeva: Umbite and paraumbite, new zirconosilicates of potassium from the Khibina alkalic massif . In: Zapiski Vserossijskogo Mineralogicheskogo Obshchestva . tape 112 , 1983, pp. 461-469 .
- Pete J. Dunn, Michael Fleischer, Carl A. Francis, Richard H. Langley, Stephen A. Kissin, James E. Shigley, David A. Vanko, Janet A. Zilczer: New Mineral Names . In: American Mineralogist . tape 69 , 1984, pp. 810–815 ( minsocam.org [PDF; 742 kB ; accessed on November 30, 2017]).
Web links
Individual evidence
- ↑ a b c d e Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p. 638 .
- ↑ Webmineral - Umbite (English)
- ↑ a b c d e f g h Umbite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( handbookofmineralogy.org [PDF; 75 kB ; accessed on November 30, 2017]).
- ↑ Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties . 6th completely revised and supplemented edition. Weise, Munich 2014, ISBN 978-3-921656-80-8 .
- ↑ a b c d e Mindat - Umbite (English)
- ^ A b Pete J. Dunn, Michael Fleischer, Carl A. Francis, Richard H. Langley, Stephen A. Kissin, James E. Shigley, David A. Vanko, Janet A. Zilczer: New Mineral Names . In: American Mineralogist . tape 69 , 1984, pp. 810–815 ( minsocam.org [PDF; 742 kB ; accessed on November 30, 2017]).
- ↑ Find location list for Umbit in the Mineralienatlas and in Mindat