Andrianovite | |
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General | |
Category | Silicate mineral, Cyclosilicate |
Formula (repeating unit) | Na12(K,Sr,Ce)3Ca6Mn3Zr3Nb(Si25O73)(O,H2O,OH)5 (original form) |
IMA symbol | Adv[1] |
Strunz classification | 9.CO.10 |
Dana classification | 64.1.2.4 |
Crystal system | Trigonal |
Crystal class | Ditrigonal pyramidal (3m) H-M symbol: (3m) |
Space group | R3m |
Unit cell | a = 14.28, c = 30.24 [Å] (approximated); Z = 3 |
Identification | |
Color | Light yellow |
Crystal habit | intergrowths (rims) with eudialyte |
Cleavage | (001), imperfect |
Fracture | Step-like |
Tenacity | Brittle |
Mohs scale hardness | 5 |
Luster | Vitreous |
Streak | White |
Diaphaneity | Transparent |
Density | 2.93 (measured), 3.02 (calculated) |
Optical properties | Uniaxial (−) |
Refractive index | nω = 1.62, nε = 1.62 (approximated) |
Pleochroism | None |
Ultraviolet fluorescence | No |
Common impurities | Sr, Ce, Fe |
References | [2][3] |
Andrianovite is a very rare mineral of the eudialyte group,[2] with formula Na12(K,Sr,Ce)6Ca6(Mn,Fe)3Zr3NbSi(Si3O9)2(Si9O27)2O(O,H2O,OH)5.[3][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.[4] Andrianovite is unique among the eudialyte group in being potassium-rich (other eudialyte-group species with essential K are davinciite and rastsvetaevite[2]). It is regarded as potassium analogue of kentbrooksite,[3] but it also differs from it in being oxygen-dominant rather than fluorine-dominant.[2] Also, the coordination number of Na in this representative is enlarged from 7 to 9. The name of the mineral honors Russian mathematician and crystallographer Valerii Ivanovich Andrianov.[3]