Andrianovite
Rare cyclosilicate mineral
From Wikipedia, the free encyclopedia
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]
| Andrianovite | |
|---|---|
Andrianovite found in Russia | |
| General | |
| Category | Silicate mineral, Cyclosilicate |
| Formula | 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] |
Occurrence and association
Andrianovite was discovered in pegmatites of Koashva open pit, Khibiny massif, Kola Peninsula. Russia. It coexists with aegirine, lamprophyllite, lomonosovite, microcline, mosandrite, natrolite, sodalite (silicates) and villiaumite.[3]
