Umbozerite

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Umbozerite
Umbozerite0.jpg
Radial umbozerite (red arrow), Karnasurt Mountain, Lowosero Tundra Massif, Russia
General and classification
other names

IMA 1973-039

chemical formula Na 3 Sr 4 ThSi 8 (O, OH) 24
Mineral class
(and possibly department)
Silicates and Germanates
System no. to Strunz
and to Dana
9.HG.15 ( 8th edition : VIII / A.10)
78.07.17.01
Crystallographic Data
Crystal system amorphous
Frequent crystal faces pseudo-tetragonal
Physical Properties
Mohs hardness 5
Density (g / cm 3 ) measured: 3.6
Cleavage Please complete!
Break ; Tenacity clamshell; brittle
colour bottle green, greenish brown to brown
Line color Please complete!
transparency transparent to translucent
shine Glass gloss
radioactivity radioactive
Crystal optics
Refractive index n  = 1.640
Other properties
Special features metamict

Umbozerite is a very rare mineral from the mineral class of " silicates and germanates " with the chemical composition Na 3 Sr 4 ThSi 8 (O, OH) 24 and usually develops needle-shaped, prismatic crystals up to about 1.5 cm in size or irregularly shaped curved inclusions. The surfaces of the bottle-green or greenish-brown to brown crystals have a glass-like sheen and are transparent to translucent.

Etymology and history

Umbozerite was discovered in 1973 on the Karnasurt mountain in the Lowosero Tundra massif on the Kola peninsula in Russia , among others the Russian mineralogist Alexander Khomyakov (* 1933) from the Institute for Geology of Ore Deposits, Petrography, Mineralogy and Geochemistry in Moscow was involved in the research involved. Umbozerit was named after the nearby Umbosero Lake. Type material of the mineral is in the Mining Institute St. Petersburg (Catalog No. 992/1), in the Fersman Museum (named after Alexander Evgenjewitsch Fersman ) in Moscow (Catalog No. 75150) and in the Mines ParisTech ( École des mines ) kept in Paris , France .

classification

In the outdated, but partly still in use 8th edition of the mineral classification according to Strunz , umbozerite belonged to the mineral class of "silicates and germanates" and there to the department of "island silicates (nesosilicates)", where it was the only member of the unnamed group VIII / A.10 educated.

The 9th edition of Strunz's mineral systematics, which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), classifies umbozerite in the “Unclassified Silicates” department. This is further subdivided according to the metals occurring in the compound, so that the mineral can be found according to its composition in the sub-section "With REE , Th ", where it is also the only member of the unnamed group 9.HG.15 .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns umbozerite to the class of "silicates and Germanates" and there in the department of "unclassified silicate minerals". Here it can be found in the unnamed group 78.07.17 within the sub-section "Unclassified Silicates: Completely Unclassified Silicates".

Crystal structure

Due to the radioactivity, it has only been found metamict , that is, its crystal lattice has been destroyed. As an amorphous substance, it has no crystal structure.

properties

The mineral is by its thorium content of about 18.4% radioactively and has a specific activity of about 8.24 k Bq / g (compared to natural potassium 0.0312 kBq / g).

Education and Locations

Umbozerite forms in the upper (apical) area of ​​a differentiated alkali rock massif under pneumatolytic to hydrothermal conditions in tunnels that set through alkaline rocks. Begleitminerale include ussingite , sphalerite , Belovit , Pektolith , lorenzenite and (beta) lomonosovit . So far (as of 2016) umbozerite could only be found at its type locality on the Karnasurt mountain in the Lowosero tundra massif and on the Alluaiw mountain (Umbozero mine).

See also

Web links

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

Individual evidence

  1. a b c Mindat Umbozerite
  2. a b c d Webmineral - Umbozerite (English)
  3. a b c d Umbozerite , In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America , 2001 ( PDF 70.7 kB )
  4. Frank C. Hawthorne: Who's Who in Mineral Names: Alexander Khomyakov, Rocks & Minerals ( PDF / HTML )
  5. [1] Es'kova EM, EI Semenov, Khomyakov AP, AN Mer'kov, Lebedeva SI, Dubakina LS (1974) Umbozerite - a new mineral. Doklady Akademii Nauk SSSR 216, 169–171 (Russian)