Xenotime
| Xenotime | |
|---|---|
 |
|
| General and classification | |
| other names |
Ytterspat or Ytterspath |
| chemical formula | (Y, Yb) [PO 4 ] |
|
Mineral class (and possibly department) |
Phosphates, arsenates and vanadates |
|
System no. to Strunz and to Dana |
8.AD.35 Xenotime Group ( 8th edition : VII / A.14) April 38, 2011. Xenotime group |
| Crystallographic Data | |
| Crystal system | tetragonal |
| Crystal class ; symbol | ditetragonal-dipyramidal; 4 / m 2 / m 2 / m |
| Space group | I 4 1 / amd (No. 141) |
| Lattice parameters | a = 6.89 Å ; c = 6.04 Å |
| Formula units | Z = 4 |
| Physical Properties | |
| Mohs hardness | 4 to 5 |
| Density (g / cm 3 ) | 4.5 |
| Cleavage | Please complete |
| colour | gray, brown, yellow, green |
| Line color | White |
| transparency | transparent to opaque |
| shine | Glass gloss to resin gloss |
| radioactivity | some Xenotime are weakly radioactive |
Xenotime , outdated also known as Ytterspat or Ytterspath , is the general name for a rather seldom occurring mixed crystal row of the minerals Xenotime- (Y) and Xenotime- (Yb) from the mineral class of " Phosphates , Arsenates and Vanadates ". Both end links of this mixed series and thus also their mixed crystals crystallize in the tetragonal crystal system . Their chemical composition is indicated with Y [PO 4 ] or Yb [PO 4 ], the general formula of the mixed series is accordingly (Y, Yb) [PO 4 ].
Xenotime form prismatic or tabular crystals , but also granular aggregates in the colors gray, brown, yellow or green.
Etymology and history
The word xenotime is derived from the Greek κευός KENOS for "vain", "apparently" and τιμή Time "value", "price" and means "apparent value". The name alludes to the fact that the yttrium contained in the mineral was mistakenly mistaken for a new element.
Xenotim was first found in 1832 in the quarries on the island of Hidra (formerly Hitterø) in Norway, about 10 km southwest of Flekkefjord . Xenotim- (Y) was first described by François Sulpice Beudant and Xenotim- (Yb) in 1999 by Harvey M. Buck, Mark A. Cooper, Petr Černý, Joel D. Grice and Frank C. Hawthorne .
classification
Already in the now outdated, but still in use 8th edition of the mineral systematics according to Strunz , xenotime (Y) and xenotime (Yb) belonged to the mineral class of "phosphates, arsenates and vanadates" and there to the department of "anhydrous phosphates without foreign anions " , where together with Chernovit- (Y) , Pretulit , Wakefieldit- (Ce) and Wakefieldit- (Y) they form the "Xenotime group" with the system no. VII / A.14 .
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 assigns xenotime (Y) and xenotime (Yb) to the class of "phosphates, arsenates and vanadates" and there into the Division of “phosphates, etc.” without additional anions; without H 2 O “. However, this section is further subdivided according to the size of the cations involved , so that the two minerals can be found according to their composition in the sub-section “With only large cations”, where they are named after the “Xenotime group” with the system no. 8.AD.35 and the other members Chernovit- (Y), Klinobisvanit , Dreyerit , Pretulit, Wakefieldit- (Ce), Wakefieldit- (La) and Wakefieldit- (Y).
The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns xenotime (Y) and xenotime (Yb) to the class of "phosphates, arsenates and vanadates" and there in the department of "anhydrous phosphates etc.". Here they are named after the "Xenotim Group (Tetragonal: I 4 1 / amd )" with the system no. 04/38/11. to be found within the subsection of " Anhydrous phosphates etc., A + XO 4 ".
Crystal structure
Xenotime- (Y) crystallizes tetragonally in the space group I 4 1 / amd (space group no. 141) with the lattice parameters a = 6.89 Å and c = 6.04 Å as well as four formula units per unit cell .
Xenotime- (Yb) also crystallizes tetragonally in the space group I 4 1 / amd (space group no. 141) with the lattice parameters a = 6.87 Å and c = 6.00 Å and four formula units per unit cell .
properties
As with other minerals that contain rare earth metals , part of the yttrium can be substituted by uranium or thorium , depending on the deposit . This results in a slight radioactivity . The specific activity of the xenotime (Yb) is given as about 1.446 k Bq / g (for comparison: natural potassium 31.2 Bq / g).
Education and Locations
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The xenotime minerals form either magmatic in granites or pegmatites or hydrothermally in the veins of the mountains. After metamorphosis in gneiss and subsequent sedimentation , Xenotime can also be found in soap deposits .
Localities lie among others in Brazil , in the city of Ishikawa in the prefecture of Fukushima in Japan , on Madagascar in Kragerø and on the island of Hidra (formerly Hitterø) in Norway in Ytterby in Sweden and in the United States .
See also
Individual evidence
- ↑ a b c d e 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. 436 .
- ↑ Webmineral - Xenotime- (Yb)
literature
- Petr Korbel, Milan Novák: Encyclopedia of Minerals . Nebel Verlag GmbH, Eggolsheim 2002, ISBN 3-89555-076-0 , p. 157 .
- Martin Okrusch, Siegfried Matthes: Mineralogy: An introduction to special mineralogy, petrology and deposit science . 7th edition. Springer Verlag, Berlin, Heidelberg, New York 2005, ISBN 3-540-23812-3 , pp. 76 .
