Carbokentbrooksite
| Carbokentbrooksite | |
|---|---|
| General | |
| Category | Silicate mineral, Cyclosilicate |
| Formula (repeating unit) | (Na,[])12(Na,Ce)3Ca6Mn3Zr3Nb(Si25O73)(OH)3(CO3)•H2O (original form) |
| Strunz classification | 8/E.25-32 |
| Dana classification | 64.1.2.3 |
| Crystal system | Trigonal, R3m' |
| Unit cell | a=14.24, c=30.04 [Å] |
| Identification | |
| Color | Yellow, yellow-orange |
| Crystal habit | rhombohedra (cores of zoned crystals) |
| Crystal symmetry | Trigonal - Ditrigonal Pyramidal (3m) |
| Cleavage | None |
| Fracture | Conchoidal |
| Tenacity | Brittle |
| Mohs scale hardness | 5 |
| Luster | Vitreous |
| Streak | White |
| Diaphaneity | Transparent |
| Density | 3.14 (measured) |
| Optical properties | Uniaxial (-) |
| Refractive index | nω=1.65, nε=1.64 (approximated) |
| Pleochroism | None |
| Ultraviolet fluorescence | No |
| References | [1][2] |
Carbokentbrooksite is a very rare mineral of the eudialyte group,[1] with formula (Na,[])12(Na,Ce)3Ca6Mn3Zr3NbSiO(Si9O27)2(Si3O9)2(OH)3(CO3).H2O.[2] The original formula was extended to show the presence of cyclic silicate groups and silicon at the M4 site, according to the nomenclature of eudialyte group.[3] Carbokenbrooksite characterizes in being carbonate-rich (the other eudialyte-group species with essential carbonate are zirsilite-(Ce), golyshevite, and mogovidite). It is also sodium rich, being sodium equivalent of zirsilite-(Ce),[1] with which it is intimately associated.[2]
Occurrence and association
Carbokentbrooksite and zirsilite-(Ce) are found as replacements of grains and crystals of eudialyte.[1] They occur in pegmatites of Darai-Pioz alkaline massif, Tajikistan - a locality known for many rare minerals.[4] The minerals are associated with aegirine, ekanite, microcline, polylithionite, quartz, stillwellite-(Ce) (silicates), pyrochlore-group mineral, fluorite, calcite, and galena.[2]
Notes on chemistry
Beside the elements given in the formula, carbokentbrooksite contains admixtures of lanthanum, strontium, neodymium, iron, yttrium, titanium, potassium, chlorine, and praseodymium. Carbokentbrooksite and zirsilite-(Ce) are chemically similar.[2]
Notes on structure
Carbokentbrooksite is isostructural with kentbrooksite.[2]
References
- 1 2 3 4 Mindat, Carbokentbrooksite, http://www.mindat.org/min-25674.html
- 1 2 3 4 5 6 Khomyakov, A.P., Dusmatov, V.D., Ferraris, G., Gula, A., Ivaldi, G., and Nechelyustov, G.N., 2003: Zirsilite-(Ce), (Na,[])12(Ce,Na)3Ca6Mn3Zr3Nb(Si25O73)(OH)3(CO3)•H2O, and carbokentbrooksite (Na,[])12(Na,Ce)3Ca6Mn3Zr3Nb(Si25O73)(OH)3(CO3)•H2O - two new eudialyte-group minerals from the Dara-i-Pioz alkaline massif, Tajikistan. Zapiski Vserossiyskogo Mineralogicheskogo Obshchestva 132(5), 40–51 (in Russian, with English abstract); in: Jambor, J.I, and Roberts, A.C., 2004: New mineral names. American Mineralogist 89(11-12), 1826-1834
- ↑ Johnsen, O., Ferraris, G., Gault, R.A., Grice, D.G., Kampf, A.R., and Pekov, I.V., 2003. The nomenclature of eudialyte-group minerals. The Canadian Mineralogist 41, 785-794
- ↑ "Darai-Pioz Glacier (Dara-i-Pioz; Dara-Pioz), Alai Range (Alayskiy), Tien Shan Mtn, Region of Republican Subordination, Tajikistan - Mindat.org". Mindat.org. Retrieved 2016-03-11.