Rastsvetaevite

Rastsvetaevite
	Tiny dark pink grains of rastsvetaevite in matrix. Field of view 3 mm. From: Rasvumchorr Mt, Khibiny Massif, Murmansk Oblast, Russia
General
Category	Silicate mineral, Cyclosilicate
Strunz classification	9.CO.10
Dana classification	64.1b.1.2
Crystal system	Trigonal
Crystal class	Ditrigonal pyramidal (3m) ; H-M symbol: (3m)
Space group	R3m
Unit cell	a = 14.25, c = 60.97 [Å] (approximated); Z = 3
Identification
Color	Reddish-pink
Crystal habit	irregular grains
Fracture	Conchoidal
Tenacity	Brittle
Mohs scale hardness	5-6
Luster	Vitreous
Streak	White
Diaphaneity	Transparent
Specific gravity	2.86
Optical properties	Uniaxial (+)
Refractive index	nω=1.60 nε = 1.60 (approximated)
References	[1]

Rastsveatevite is a rare mineral of the eudialyte group with the formula Na₂₇K₈Ca₁₂Fe₃Zr₆Si₄[Si₃O₉]₄[Si₉O₂₇]₄(O,OH,H₂O)₆Cl₂. Its structure is modular.[2] It is only the third member of the group after andrianovite and davinciite with essential (site-dominating) potassium.[1] Potassium and sodium enter both N4 and M2 sites.[3] The mineral is named after Russian crystallographer Ramiza K. Rastsvetaeva.[1]

Occurrence and association

Rastsvetaevite was originally found in hyperagpaitic (ultra-alkaline) pegmatite at Mt. Rasvumchorr, Khibiny massif, Kola Peninsula, Russia. Associated minerals are aegirine, nacaphite, nepheline, natrite, schcherbakovite, sodalite, villiaumite, and rasvumite.[1]

Notes on crystal structure

The c unit cell parameter in rastsvetaevite is doubled.[1]

References

Mindat, http://www.mindat.org/min-26586.html
Khomyakov, A.P.; Nechelyustov, G.N.; Arakcheeva, A.V. (2006). "Rastsvetaevite, Na₂₇K₈Ca₁₂Fe₃Zr₆Si₄[Si₃O₉]₄[Si₉O₂₇]₄(O,OH,H₂O)₆Cl₂, a new mineral with a modular eudialyte-like structure and crystal-chemical systematics of the eudialyte group". Proceedings of the Russian Mineralogical Society. 135 (1): 49–65.
Johnsen, O.; Ferraris, G.; Gault, R. A.; Grice, J. D.; Kampf, A. R.; Pekov, I. V. (2003-06-01). "The nomenclature of eudialyte-group minerals". The Canadian Mineralogist. 41 (3): 785–794. doi:10.2113/gscanmin.41.3.785. ISSN 0008-4476.

This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.

[M-1] Mindat, http://www.mindat.org/min-26586.html

[2] Khomyakov, A.P.; Nechelyustov, G.N.; Arakcheeva, A.V. (2006). "Rastsvetaevite, Na₂₇K₈Ca₁₂Fe₃Zr₆Si₄[Si₃O₉]₄[Si₉O₂₇]₄(O,OH,H₂O)₆Cl₂, a new mineral with a modular eudialyte-like structure and crystal-chemical systematics of the eudialyte group". Proceedings of the Russian Mineralogical Society. 135 (1): 49–65.

[3] Johnsen, O.; Ferraris, G.; Gault, R. A.; Grice, J. D.; Kampf, A. R.; Pekov, I. V. (2003-06-01). "The nomenclature of eudialyte-group minerals". The Canadian Mineralogist. 41 (3): 785–794. doi:10.2113/gscanmin.41.3.785. ISSN 0008-4476.