Lomonosovite is a phosphate–silicate mineral with the idealized formula Na10Ti4(Si2O7)2(PO4)2O4[2] early Na5Ti2(Si2O7)(PO4)O2 or Na2Ti2Si2O9*Na3PO4.[3]
The mineral was discovered by V.I. Gerasimovskii [5] in Lovozersky agpaitic massif. Named for Mikhail Lomonosov - famous Russian poet, chemist and philosopher, but the earlier - mining engineer.[6]
Crystal structureedit
According to X-ray data, lomonosovite structure was determined is triclinic unit cell with parameters: a = 5.44 Å, b = 7.163 Å, c = 14.83 Å, α = 99°, β = 106°, and γ = 90°, usually centrosymmetric (sp. gr. P-1),[7] but acentric varieties (polytype) are also reported.[4]
The crystal structure of lomonosovite is based on three-layer HOH packets consisting of a central octahedral O layer and two outer heteropolyhedral H layers. Ti- and Na centered octahedra are distinguished in the O layer, whereas the H layers are composed of Ti-centered octahedra and Si2O7 diorthogroups, (like in other heterophyllosilicates, for example lamprophyllite). The interpacket space includes Na+ cations and PO43- anions.[7]
Propertiesedit
Lomonosovite forms lamellar and tabular crystals with perfect cleavage. It is macroscopically brown, from cinnamon-brown to black. It is transparent in thin plates. The luster vitreous to adamantine.
Its pleochroism is strong from colorless to brown. The refractive index is = 1.654-1.670 = 1.736 - 1.750 =1.764-1.778 2V=56-69.[3]
Accessory mineral of peralkaline agpaitic nepheline syenites (like Khibina and Lovozero massif, Russia, Ilimaussaq intrusion, Greenland) important mineral of agpaitic pegmatites and peralkaline fenites.[3]
lomonosovite, phosphate, silicate, mineral, with, idealized, formula, na10ti4, si2o7, early, na5ti2, si2o7, na2ti2si2o9, na3po4, generalcategorymineralformula, repeating, unit, na10ti4, si2o7, 2o4ima, symbollom, crystal, systemtriclinicunit, cella, identificat. Lomonosovite is a phosphate silicate mineral with the idealized formula Na10Ti4 Si2O7 2 PO4 2O4 2 early Na5Ti2 Si2O7 PO4 O2 or Na2Ti2Si2O9 Na3PO4 3 LomonosoviteGeneralCategoryMineralFormula repeating unit Na10Ti4 Si2O7 2 PO4 2O4IMA symbolLom 1 Crystal systemTriclinicUnit cella 5 49 A b 7 11 A c 14 5 A a 101 b 96 g 90 IdentificationCleavagePerfectFractureIrregularTenacityBrittleMohs scale hardness3 4Density3 12 3 15Optical propertiesBiaxial Refractive indexna 1 670 nb 1 750 ng 1 778Birefringence0 1082V angle56 The main admixtures are niobium up to 11 8 Nb2O5 manganese up to 4 5 MnO and iron up to 2 8 4 Contents 1 Discovery and name 2 Crystal structure 3 Properties 4 Origin 5 ReferencesDiscovery and name editThe mineral was discovered by V I Gerasimovskii 5 in Lovozersky agpaitic massif Named for Mikhail Lomonosov famous Russian poet chemist and philosopher but the earlier mining engineer 6 Crystal structure editAccording to X ray data lomonosovite structure was determined is triclinic unit cell with parameters a 5 44 A b 7 163 A c 14 83 A a 99 b 106 and g 90 usually centrosymmetric sp gr P 1 7 but acentric varieties polytype are also reported 4 The crystal structure of lomonosovite is based on three layer HOH packets consisting of a central octahedral O layer and two outer heteropolyhedral H layers Ti and Na centered octahedra are distinguished in the O layer whereas the H layers are composed of Ti centered octahedra and Si2O7 diorthogroups like in other heterophyllosilicates for example lamprophyllite The interpacket space includes Na cations and PO43 anions 7 Properties editLomonosovite forms lamellar and tabular crystals with perfect cleavage It is macroscopically brown from cinnamon brown to black It is transparent in thin plates The luster vitreous to adamantine Its pleochroism is strong from colorless to brown The refractive index is a displaystyle alpha nbsp 1 654 1 670 b displaystyle beta nbsp 1 736 1 750 g displaystyle gamma nbsp 1 764 1 778 2V 56 69 3 Hardness 3 4 Density 3 12 3 15 3 Origin editAccessory mineral of peralkaline agpaitic nepheline syenites like Khibina and Lovozero massif Russia Ilimaussaq intrusion Greenland important mineral of agpaitic pegmatites and peralkaline fenites 3 References edit Warr L N 2021 IMA CNMNC approved mineral symbols Mineralogical Magazine 85 3 291 320 Bibcode 2021MinM 85 291W doi 10 1180 mgm 2021 43 S2CID 235729616 COMMISSION ON NEW MINERALS a b c d Handbook of mineralogy PDF a b Rastsvetaeva Zaitsev Pekov 2020 Crystal Structure of Niobium Rich Lomonosovite with Symmetry P1 from the Khibiny Massif Kola Peninsula Crystallography Reports 65 3 22 427 Bibcode 2020CryRp 65 422R doi 10 1134 S1063774520030268 S2CID 219784165 a href Template Cite journal html title Template Cite journal cite journal a CS1 maint multiple names authors list link Gerasimovskii V I Lomonosovite a new mineral Dokl Akad Nauk SSSR 70 Maburg Song of Yu Lores a b Rastsvetaeva Simonov Belov 1971 Crystalline structure of lomonosovite Na5Ti2 Si2O7 PO4 O2 Dokl Akad Nauk SSSR 197 1 81 84 a href Template Cite journal html title Template Cite journal cite journal a CS1 maint multiple names authors list link nbsp This article about a specific silicate mineral is a stub You can help Wikipedia by expanding it vte Retrieved from https en wikipedia org w index php title Lomonosovite amp oldid 1170029607, wikipedia, wiki, book, books, library,
