Proshchenkoit- (Y)
| Proshchenkoit- (Y) | |
|---|---|
_-_Tommot,_Yakutia,_Russia.jpg) |
|
| General and classification | |
| other names |
IMA 2008-007 |
| chemical formula | (Y, REE, Ca, Na, Mn) 15 Fe 2+ Ca (P, Si) Si 6 B 3 (O, F) 48 |
|
Mineral class (and possibly department) |
Silicates and Germanates |
|
System no. to Strunz and to Dana |
9.AJ.35 54.03.01.03 |
| Crystallographic Data | |
| Crystal system | trigonal |
| Crystal class ; symbol | ditrigonal-pyramidal; 3 m |
| Space group | R 3 m (No. 160) |
| Lattice parameters | a = 10.75 Å ; c = 27.40 Å Please complete the source as an individual reference |
| Formula units | Z = 3 Please complete the source as an individual reference |
| Physical Properties | |
| Mohs hardness | 5 |
| Density (g / cm 3 ) | measured: 4.72; calculated: 4.955 |
| Cleavage | no |
| Break ; Tenacity | uneven to scalloped, brittle |
| colour | brownish to reddish, in fragments orange-yellow |
| Line color | light brown |
| transparency | transparent to translucent |
| shine | Glass gloss to fat gloss |
| radioactivity | weakly radioactive |
| Crystal optics | |
| Refractive indices |
n ω = 1.734 (2) n ε = 1.728 (2) |
| Optical character | uniaxial negative |
Proshchenkoit- (Y) is a very rarely occurring mineral from the mineral class of " silicates and germanates " with the chemical composition (Y, REE, Ca, Na, Mn) 15 Fe 2+ Ca (P, Si) Si 6 B 3 ( O, F) 48 .
Proshchenkoit- (Y) crystallizes in the trigonal crystal system and has so far only in the form of granular aggregates with irregularly shaped, transparent to translucent single crystals of brownish to reddish color with light brown stroke color to be found.
Etymology and history
Proshchenkoit- (Y) was first discovered in 1966 in the Tommot massif in the northeastern Republic of Sakha ( Yakutia ) of today's Russian Federation and also described as a find, but without a name. It was analyzed, fully described and recognized as a new mineral of the Vicanite group in 2008 by Gunnar Raade , Joel D. Grice , M. Erambert, Per Kristiansson and Thomas Witzke , who named the mineral after its discoverer, the Russian mineralogist Evgeni Grigoryevich Proschtschenko (Russian: Евгений Григорьевич Прощенко , 1929–1996).
The mineral and the chosen name Proshchenkoit- (Y) were acquired by the International Mineralogical Association (IMA) in the same year under the internal entry no. IMA2008-007 recognized. Type material of the mineral is in the Naturhistorisk Museum ( Natural History Museum, University of Oslo , register no. 42029)
classification
Since the Proshchenkoit- (Y) was only recognized as an independent mineral in 2008, it is not listed in the 8th edition of the Strunz mineral classification, which has been outdated since 2001 .
The 9th edition of the Strunz'schen mineral systematics , which has been in effect since 2001 and is used by the IMA, assigns the Proshchenkoit- (Y) to the class of "silicates and germanates" and there in the department of " island silicates (nesosilicates)". This is further subdivided according to the possible presence of additional anions and the coordination number of the cations involved , so that the mineral can be divided into corners in the subdivision of "Island silicates with BO 3 triangles and / or B [4] -, Be [4] tetrahedra" SiO 4 ”can be found, where together with Hundholmenit- (Y) , Okanoganit- (Y) and Vicanit- (Ce) the“ Vicanite group ”with the system no. 9.AJ.35 forms.
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns the Proshchenkoit- (Y) to the class of "silicates and Germanates", but there in the more finely divided department of "island silicates: borosilicates and some beryllosilicates with (BO 3 ) " a. Here it is, also together with Vicanite- (Ce) and Hundholmenit- (Y), in the "Vicanite group" with the system no. 54.03.01 to be found in the subsection " Island silicates: borosilicates and some beryllosilicates ".
Chemism
The analysis of the material obtained from the rare earth and niobium deposit Tommot ( Yakutia ) resulted in the following empirical formula:
(Y 3.70 REE 7.54 Ca 1.55 Na 1.16 Mn 0.77 Th 0.10 Pb 0.01 ) Σ14.83 (Fe 0.83 2+ Mn 0.15 Ti 0.02 ) Σ1 , 00 Ca 1.00 (P 0.70 Si 0.26 As 0.04 ) Σ1.00 Si 6.05 B 3.20 (O 34.55 F 13.45 ) Σ48
However, this may change slightly depending on the composition of other samples.
Crystal structure
Proshchenkoit- (Y) crystallizes trigonally in the space group R 3 m (space group no. 160) with the lattice parameters a = 10.75 Å and c = 27.40 Å and 3 formula units per unit cell .
properties
Proshchenkoit- (Y) is classified as weakly radioactive due to its content of rare earth metals of up to 40% and thorium of up to 0.9% and has a specific activity of about 387 Bq / g (for comparison: natural Potassium 31.2 Bq / g).
Education and Locations
Proshchenkoit- (Y) forms in pegmatites , often as inclusions in crystalline schist and aegirin - gneiss . In these it is mostly to be found scattered in nest-shaped deposits or thin veins. Accompanying minerals include alkali amphiboles , britholite (Ce) , chevkinite (Ce) , fergusonite , fluorite , gadolinite , molybdenite and pyrite .
So far (status: 2010) the mineral could only be detected at its type locality Tommotskii massif (Yakutia).
See also
literature
- Gunnar Raade, Joel D. Grice, Muriel Erambert, Per Kristiansson, Thomas Witzke: Proshchenkoite- (Y) from Russia - a new mineral species in the vicanite group: descriptive data and crystal structure . In: Mineralogical Magazine . tape 72 , 2008, p. 1071-1082 , doi : 10.1180 / minmag.2008.072.5.1071 .
Web links
Individual evidence
- ↑ a b Webmineral - Proshenkoite- (Y) (English)
- ↑ Mindat - Proshchenkoite- (Y) (English)