Kristiansenite

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Kristiansenite
Kristiansenite-185002.jpg
White Kristiansenite crystals in a 1 mm wide group from the pegmatite Heftetjern near Tørdal in Drangedal , Telemark , Norway
General and classification
other names

IMA 2000-051

chemical formula Ca 2 ScSn (Si 2 O 7 ) (Si 2 O 6 OH)
Mineral class
(and possibly department) 		Silicates and germanates - group silicates
System no. to Strunz
and to Dana 		9.BC.30 ( 8th edition : VIII / C.01)
56.02.04.16
Crystallographic Data
Crystal system triclinic
Crystal class ; symbol triklin-pedial; 1
Space group P 1 (No. 1)Template: room group / 1
Lattice parameters a  = 10.028  Å ; b  = 8.408 Å; c  = 13.339 Å,
α  = 90.01 °; β  = 109.10 °; γ  = 90.00 °
Formula units Z  = 4
Frequent crystal faces {010}
Twinning polysynthetic according to {010} with twin stripes
Physical Properties
Mohs hardness 5.5 to 6
Density (g / cm 3 ) 3.64 (calculated); > 3.3 (measured)
Cleavage very perfect after {001}
Break ; Tenacity uneven; brittle
colour colorless, white or slightly yellowish
Line color White
transparency translucent to translucent
shine Glass gloss
Crystal optics
Refractive index n  = 1.74
Optical character biaxial, orientation unknown

Kristiansenite is a very rarely occurring mineral from the mineral class of "silicates and germanates" with the idealized chemical composition Ca 2 ScSn (Si 2 O 7 ) (Si 2 O 6 OH) and is therefore chemically a calcium - scandium - tin - group silicate . It crystallizes in the triclinic crystal system and develops colorless or white, tapering or pointed crystals up to 2 mm in size.

The type locality of the mineral is the Cleavelandite - Amazonite - Pegmatite "Heftetjern" in Drangedal , Telemark , Norway , located 4.3 km northwest of Tørdal between Høydalen and Skarsfjell, where high quality amazonite has been mined since the early 1970s. This pegmatite, which is rich in Sc-containing or Sc-bearing minerals, is also the type locality for agakhanovite- (Y) , heftetjernite and oftedalite, as well as the as yet unnamed (OH) -dominant analogue of gadolinite- (Y) .

Etymology and history

On May 6, 1998, during his first visit to the Heftetjern pegmatite , Roy Kristiansen found a hand specimen with feldspar, quartz and biotite which contained yellowish-gray prismatic crystals in cavities together with cerium -containing epidote and calcium -containing hingganite- (Y) proved to be an unknown mineral in preliminary X-ray diffractometric examinations. After extensive further analyzes, the results could be submitted to the International Mineralogical Association (IMA), which recognized it as a new mineral in February 2001 without a dissenting vote. After Giovanni Ferraris , Angela Gula , Gabriella Ivaldi and Massimo Nespolo described the crystal structure of the new mineral in the German science magazine Zeitschrift für Kristallographie - Crystalline Materials in mid-August 2001 , an international research team led by the Norwegian geologist Gunnar Raade published the first scientific description of the new mineral in 2002 Minerals in the Austrian science magazine Mineralogy and Petrology . They named the mineral as Kristiansenite after its finder, the Norwegian amateur mineralogist Roy Kristiansen (* 1943).

Type material of the mineral is kept in the collection of the Geological Museum at the University of Oslo in Oslo , Norway .

classification

In the meanwhile outdated, but still in use 8th edition of the mineral systematics according to Strunz , the Kristiansenite belonged to the mineral class of "silicates and germanates" and there to the department of " group silicates (sorosilicates)", where together with Gittinsit , Keiviit- (Y) , Keiviit- (Yb) , Percleveit- (Ce) , Rowlandite- (Y) , Thortveitite and Yttrialite- (Y) the "Thortveitite series" with the system no. VIII / C.01 .

The 9th edition of Strunz's mineral systematics , which has been in force since 2001 and is used by the International Mineralogical Association (IMA), also classifies Kristiansenite in the "group silicates" department. However, this is now further subdivided according to the type of silicate building blocks, the possible presence of further anions and the coordination of the cations , so that the mineral can be classified according to its composition and structure in the subsection “Si 2 O 7 groups without non- tetrahedral anions; Cations in octahedral [6] and / or other coordination ”can be found, where it is the only member of the unnamed group 9.BC.30 .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns Kristiansenite to the class of "silicates and germanates" and there in the department of " group silicates : Si 2 O 7 groups and O, OH, F and H2O". Here he is together with Baghdadit , Burpalit , Cuspidin , Låvenit , Wöhlerit , Niocalit , Hiortdahlit , Rosenbuschit , Hainit , Janhaugit , Jennit , Komarovit , Natrokomarovit , Suolunit , Mongolite , Kochit and Marianoit in the "Cuspidin-Wohlerit-Gruppe" with the system -No. 56.02.04 within the subsection " Group silicates: Si2O7 groups and O, OH, F and H 2 O with cations in [4] and / or> [4] coordination ".

Chemism

Analysis of the Kristiansenite from Heftetjern gave mean values ​​of 0.41% Na 2 O, 0.06% K 2 O, 18.45% CaO, 0.35% Al 2 O 3 , 8.11% Sc 2 O 3 , 1 , 98% Fe 2 O 3 , 40.76% SiO 2 , 0.08% TiO 2 , 0.43% ZrO 2 , 27.33% SnO 2 and (2.04)% H 2 O (determined by difference) . On the basis of seven (O + OH), the empirical formula (Ca 0.96 Na 0.04 ) Σ = 1.00 (Sn 0.53 Sc 0.34 Fe 0.07 Al 0.02 Zr 0 , 01 ) Σ = 0.97 Si 1.98 [O 6.34 (OH) 0.66 ] Σ = 7.00 . The ideal formula for the mineral, on the other hand, is Ca 2 ScSn (Si 2 O 7 ) (Si 2 O 6 OH), which has contents of 19.30% CaO, 11.86% Sc 2 O 3 , 41.36% SiO 2 , 25 , 93% SnO 2 and 1.55% H 2 O required.

Kristiansenite is chemically similar to thortveitite, Sc 2 (Si 2 O 7 ), but contains calcium and tin on the cation side and a protonated disilicate group with an additional hydrogen atom (Si 2 O 6 OH) on the anion side in addition to the normal Si 2 O 7 disilicate group . Kristiansenite also forms the Sc-dominant analogue of the Fe 3+ -dominated silesiaite , Ca 2 Fe 3+ Sn (Si 2 O 7 ) (Si 2 O 6 OH). Among the 19 scandium minerals recognized by the IMA today, Kristiansenite was the ninth scandium phase described in chronological order.

Crystal structure

Kristiansenite crystallizes triclinically in the space group P 1 (space group  no.1 ) with the lattice parameters a = 10.028  Å , b  = 8.408 Å, c  = 13.339 Å, α = 90.01 °, β = 109.10 ° and γ = 90 .00 ° and four formula units per unit cell . Template: room group / 1

The crystal structure of Kristiansenite contains Si 2 O 7 - double tetrahedra and isolated polyhedra from 6-coordinate Sn, Sc and Fe as well as (7 + 2) Er-coordinated Ca cations. Half of the disilicate groups contain a hydrogen atom, which is why crystalliansenite is the first mineral to contain a normal Si 2 O 7 disilicate group and a protonated disilicate group Si 2 O 6 OH at the same time . The octahedral M positions are occupied as follows: M 1 = 0.99Sn + 0.1Fe, M 2 = 0.61Sn + 0.39Sc, M 3 = 0.30Sn + 0.50Sc + 0.20Fe, M 4 = 0.17Sn + 0.63Sc + 0.20Fe. The octahedra M are isolated from one another and alternate with the disilicate groups along the (10 1 ) faces. Two independent and relatively short O… O hydrogen bonds connect the rows of sorosilicate groups. Kristiansenite was the first mineral with this crystal structure. It is isotypic to its Fe 3+ analogue silesiaite, i.e. it crystallizes with the same structure as this one.

properties

morphology

Kristiansenite occurs in an amazonite pegmatite within cavities in feldspar and forms pointed, tapering crystals of up to 2 mm in length and massive aggregates of approx. 2 mm in diameter. Almost without exception, the crystals show a polysynthetic twin formation according to {010} with twin stripes. Due to this twin stripe and the matt crystal surfaces, crystal shapes could not be measured, but the Pedion {010} is present.

physical and chemical properties

Kristiansenite crystals are colorless, white or slightly yellowish as well as pale tan, but their line color is always white. The surfaces of the translucent to transparent crystals have a glass-like sheen due to the medium-high refraction of n = 1.74 , but appear matt due to the strong twin stripes.

Neither cleavage nor divisibility was observed on Kristiansenite , however, from the preferred orientation in the X-ray diffraction pattern, a cleavage according to {001} can be inferred. Due to its brittleness, the mineral breaks like amblygonite , with the fracture surfaces being uneven. The crystals have a Mohs hardness between 5.5 and 6. Kristiansenite is one of the hard minerals, stands between the reference minerals apatite (hardness 5) and orthoclase (hardness 6) and can be used with a pocket knife (apatite) or with a Already scratch the steel file (orthoclase). Since crystals of crystals sink in the heavy liquid diiodomethane , their density must be greater than 3.3 g / cm³. The calculated density for Kristiansenite is 3.64 g / cm³. Kristiansenit is neither in the long term nor in the short wavelength UV light , a fluorescent .

Education and Locations

Kristiansenite is a late hydrothermally formed mineral and crystallized in cavities in feldspar after albite and a last generation of tiny quartz crystals . Other accompanying minerals are scandiobabingtonite , scandium-containing ixiolite , hingganite (Y), cerium- containing epidote, titanite , “plumbomicrolite” and other representatives of the microlite group, bazzite , milarite , cassiterite and two unidentified tantalum minerals ( rynersonite and tantite ?). The mineral was also found in the form of colorless grains in altered Spessartine .

As a very rare mineral formation, Kristiansenite could so far (as of 2018) only be described by its type locality and five other sites. The type locality is the scandium-rich Heftetjern pegmatite ( coordinates of the pegmatite Heftetjern ), a cleavelandite-amazonite pegmatite of the mixed LCT-NYF type (LCT =  lithium , cesium , tantalum - NYF = niobium, yttrium , fluorine ), which is located not far from the Town of Tørdal is located between Høydalen and Skarsfjell in the province ( Fylke ) Telemark, Norway.

Other sites are the pegmatite "Kožichovice II" near Kožichovice not far from Třebíč , Kraj Vysočina , Moravia , Czech Republic , the granite quarry "Cava Scala dei Ratti" near Feriolo and the former quarry "Locatelli" and the "Miniera Seula" (ex Cava Montecatini), both on Monte Camoscio not far from Oltrefiume, all near Baveno , Verbano-Cusio-Ossola Province, Piedmont region , Italy , and finally the “Cadalso de los Vidrios” granite quarries near Madrid in Spain . Findings for Kristiansenite in Germany , Austria and Switzerland are not known.

use

Kristiansenite would be an important scandium ore due to its high scandium content, but due to its extreme rarity it is only of interest to mineral collectors.

See also

literature

  • Gunnar Raade, Giovanni Ferraris, Angela Gula, Gabriella Ivaldi, Franz Bernhard: Kristiansenite, a new calcium – scandium – tin sorosilicate from granite pegmatite in Tørdal, Telemark, Norway . In: Mineralogy and Petrology . tape 75 , no. 1–2 , 2002, pp. 89–99 , doi : 10.1007 / s007100200017 ( univ-lorraine.fr [PDF; 125 kB ; accessed on January 6, 2018]).
  • Roy Kristiansen: A unique assemblage of Scandium-bearing minerals from the Heftetjern-pegmatite, Tørdal, south Norway (Kongsberg Mineralsymposium 2009) . In: Norsk Bergverksmuseum Skrift . tape 41 , 2009, p. 75-104 ( nags.net [PDF; 17.3 MB ; accessed on January 3, 2018]).

Web links

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

Individual evidence

  1. ↑ a b c d e f g h i j k l m n o Gunnar Raade, Giovanni Ferraris, Angela Gula, Gabriella Ivaldi, Franz Bernhard: Kristiansenite, a new calcium – scandium – tin sorosilicate from granite pegmatite in Tørdal, Telemark, Norway . In: Mineralogy and Petrology . tape 75 , no. 1–2 , 2002, pp. 89–99 , doi : 10.1007 / s007100200017 ( univ-lorraine.fr [PDF; 125 kB ; accessed on January 6, 2018]).
  2. ^ Uwe Kolitsch, Roy Kristiansen, Gunnar Raade, Ekkehart Tillmanns: Heftetjernite, a new scandium mineral from the Heftetjern pegmatite, Tørdal, Norway . In: European Journal of Mineralogy . tape 22 , no. 2 , 2010, p. 309-316 , doi : 10.1127 / 0935-1221 / 2010 / 0022-1987 .
  3. ↑ a b c d Roy Kristiansen: A unique assemblage of Scandium-bearing minerals from the Heftetjern-pegmatite, Tørdal, south Norway (Kongsberg Mineralsymposium 2009) . In: Norsk Bergverksmuseum Skrift . tape 41 , 2009, p. 75-104 ( nags.net [PDF; 17.3 MB ; accessed on January 3, 2018]).
  4. ↑ a b Mindat - Heftetjern locality
  5. ↑ - History of the discovery of Kristiansenite
  6. ↑ Steven C. Chamberlain: Who's who in mineral names - Roy Kristiansen (b. 1943) . In: Rocks and Minerals . tape 90 , no. 1 , 2015, p. 89–90 ( nags.net [PDF; 1.1 MB ; accessed on January 6, 2018]).
  7. ↑ Giovanni Ferraris, Angela Gula, Gabriella Ivaldi, Massimo Nespolo: Crystal structure of kristiansenite: a case of class IIB twinning by metric merohedry . In: Journal of Crystallography - Crystalline Materials . tape 216 , no. 8 , 2001, p. 442–448 , doi : 10.1524 / zkri.216.8.442.20353 ( researchgate.net [PDF; 802 kB ; accessed on January 6, 2018]).
  8. ^ Joseph A. Mandarino: New Minerals (Kristiansenite on page 815) . In: The Canadian Mineralogist . tape 41 , 2003, p. 803–828 ( rruff.info [PDF; 134 kB ; accessed on January 3, 2018]).
  9. ^ Database-of-Raman-spectroscopy (RRUFF) - Kristiansenite
  10. ↑ Mindat - Number of localities for Heftetjernit
  11. ↑ a b List of sites for Heftetjernit in the Mineralienatlas and Mindat
  12. ↑ Jakub Výravský, Radek Škoda, Milan Novak: Kristiansenite, thortveitite and SCNbO 4 : Products of Ca-metasomatism of Sc-enriched columbite- (Mn) from NYF pegmatite Kožichovice II, Czech Republic (PEG2017) . In: NGF Abstracts and Proceedings . tape 2 , 2017, ISBN 978-82-8347-019-2 , pp. 169-172 .
  13. Jump up ↑ P. Prado-Herrero, J. Garcia-Guinea, E. Crespo-Feo, V. Correcher, C. Menor: First find of Kristiansenite in Spain: Comparison with the type specimen by non-descreptive techniques . In: Estudos Geológicos . tape 19 , no. 2 , 2009, p. 135-139 .
  14. ^ Mindat - Kristiansenit