Rait (mineral)

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Rait
Raite1 - Poudrette quarry, Mont Saint-Hilaire, Quebec, Canada.jpg
Gold-colored Rait "suns" on dark red-brown eudialyte from Mont Saint-Hilaire , Québec , Canada (image size: 3.7 × 2.5 mm)
General and classification
other names

IMA 1972-010

chemical formula Na 3 Mn 2+ 3 Ti 4+ 0.25 [OH | Si 4 O 10 ] 2  • 10 H 2 O
Mineral class
(and possibly department) 		Silicates and Germanates
System no. to Strunz
and to Dana 		9.EE.55 ( 8th edition : VIII / F.24)
78.05.08.01
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic 2 / m
Space group C 2 / m
Lattice parameters a  = 15.1  Å ; b  = 17.60 Å; c  = 5.290 Å
β  = 100.5 °
Formula units Z  = 2
Physical Properties
Mohs hardness 3
Density (g / cm 3 ) 2.32 to 2.39
Cleavage perfect after {100}, {010}, {001}
colour bronze, brown to yellow or pink, lavender
Line color yellow
transparency translucent
shine Glass gloss
Crystal optics
Refractive indices n α  = 1.540
n β  = 1.542
n γ  = 1.550
Birefringence δ = 0.010
Optical character biaxial negative
Axis angle 2V = 53 °
Pleochroism colorless - yellowish - golden brown
Other properties
Chemical behavior decomposes in dilute HCl or HNO 3 solution to form skeletal silica residues

The mineral Rait is a rarely occurring sheet silicate with the chemical composition Na 3 Mn 2+ 3 Ti 4+ 0.25 [OH | Si 4 O 10 ] 2  · 10 H 2 O, whereby the results of the few analyzes differ slightly.

It crystallizes in the monoclinic crystal system and forms needle-shaped crystals only a few mm long. Rait is yellow to golden brown, more rarely pink to lavender and translucent with a glass sheen. The stroke color is yellow-white. The density is 2.32 to 2.39 g / cm 3 and the Mohs hardness is 3.

Special properties

Rait is insoluble in water and decomposes in dilute hydrochloric acid and nitric acid to form skeletal silica residues.

Etymology and history

The mineral was first described in 1973 by AN Men'Kov et al. in an alkali pegmatite on the Kola Peninsula Russia . This mineral was named after the reed boat " Ra ", in honor of the international group of scientists who crossed the Atlantic on the "Ra" under the direction of Thor Heyerdahl .

classification

In the old systematics of minerals according to Strunz (8th edition) , the rait is assigned to the "chain and band silicates (inosilicates)", where it forms a separate group together with balangeroite , gageit and leukophane . Since the restructuring of Stunz's mineral system and updated analyzes of many minerals, the Rait now belongs to a different department. It can now be found in the subdivision of " phyllosilicates with simple tetrahedral networks of 6-membered rings, connected by octahedral networks or ribbons ".

The systematics of minerals according to Dana sorts the Rait as the only mineral of the group "78.05.08" in the department of " Unclassified silicates: possible phyllosilicates ".

Education and Locations

Rait (yellow, needle-like spheres), Sérandit (white prisms) and Aegirin (black prisms) from Mont Saint-Hilaire , Québec , Canada (image size: 7.0 × 4.6 mm)

Rait forms in alkali-rich pegmatites at low temperatures.

In the Yubileinaya Pegmatite type locality in the Lovozero massif on the Kola Peninsula , Russia , rait occurs on the walls of crevices and cavities along with nepheline , aegirine , mountainite , natrolite and zorite .

At Mont Saint-Hilaire in Québec , Canada , ratite is found together with aegirine , albite , nepheline , sodalite , sérandite , analcime , ankylite , epididymite , eudialyte and neadkevichite .

Further locations are not yet known.

morphology

Rait forms radial aggregates of needle-like crystals which are up to 2 mm long and 0.02 to 0.04 mm thick.

Crystal structure

Rait crystallizes in the monoclinic crystal system in the space group C2 / m with the lattice parameters a  = 15.1  Å , b  = 17.60 Å, c  = 5.290 Å and β  = 100.5 °, as well as two formula units per unit cell .

See also

Individual evidence

  1. ↑ a b c Webmineral - Raite (Engl.)
  2. ↑ a b American Mineralogist Crystal Structure Database - Raite (Eng., 1999)
  3. ↑ a b c Raite at mindat.org (engl.)
  4. ↑ Stefan Weiß: The large Lapis mineral directory . 5th edition. Christian Weise Verlag, Munich 2008, ISBN 3-921656-17-6 .
  5. ↑ Mindat - Localities for Raite
  6. ↑ American Mineralogist Crystal Structure Database - Raite (1999)

literature

  • AN Mer'Kov, IV Bussen, EA Goiko, EA Kul'chitskaya, Yu. P. Men'shikov, and AP Nedorezova (1973): Raite and zorite, new minerals from the Lovozero Tundra. Zapiski Vses. Mineral. Obshch. lO2, pp. 54-62.
  • M. Fleischer: New Mineral Names. At the. Min. 58, pp. 1113 ( PDF (559 kB) )
  • Anthony, JW, Bideaux, RA, Bladh, KW, and Nichols, MC (2000): Raite , In: Handbook of Mineralogy, American Mineralogical Society ( PDF (73 kB) )
  • Pushcharovsky DY, Pekov IV, Pluth JJ, Smith JV, Ferraris G Vinogradova SA, Arakcheeva AV, Soboleva SV, Semenov EI (1999): Raite, manganonordite- (Ce), and ferronordite- (Ce) from the Lovozero massif: Crystal structures and mineralogical geochemistry. Crystallography Reports 44, pp. 565-574 ( AMC data, American Mineralogist Crystal Structure Database )

Web links

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