Paralomonosovite (original) (raw)

Formula:

Na6◻4Ti4(Si2O7)2[PO3OH][PO2(OH)2]O2(OF)

Colour:

Yellowish-brown, rose, brown

Lustre:

Vitreous, Greasy, Pearly

Name:

First described by Gerasimovskiy and Kazakova (1962) from two pegmatites on the left and right banks of the Tyul'bnyunuai River, Lovozero massif, Kola, Russia. It was named betalomonosovite for its similarity to lomonosovite. Around the same time the name metalomonosovite was also used because the mineral was assumed to contain sodium metaphosphate. The status has been much discussed because of difficulties obtaining valid results on structure and chemical analyses. The poor quality of the crystals was related to an extensive cation and anion disorder present in the structure, including H2O (Sokolova et al. 2015). As a result it was discredited by IMA in 2013 (removed from the IMA list). Later Sokolova et al. (2015) succeeded in refining the structure. Based on their work, betalomonosovite was reapproved by IMA in 2015 (IMA 14-J) (Sokolova et al. 2015). It was renamed to paralomonosovite in 2022 by the IMA.

Samples from Pyalkimporr Mountain, Lovozero Massif were used in the study of Sokolova et al. 2015).

A Na-poor OH-bearing analogue of lomonosovite.

Betalomonosovite is a Group-IV TS-block mineral (Ti + Mg + Mn = 4 apfu). The crystal structure of betalomonosovite is an alternation of TS and I blocks of the composition Na4Ti4(Si2O7)2O2(OF) and Na2D4[PO3(OH)][PO2(OH)2], respectively (Sokolova et al. 2015).

Compare 'UM1988-04-SiOPO:CaFeHNaNbTi'.

Approved, 'Grandfathered' (first described prior to 1959)

IMA status notes:

Renamed by the IMA

IMA Formula:

Na5+xTi4(Si2O7)2[PO3(OH)]2-y[PO2(OH)2]yO2[(OH,F)2-xOz], [0<x<2, 0<y<1, 0<z<1]

Class (H-M):

1 - Pinacoidal

Cell Parameters:

a = 5.3331(7) Å, b = 14.172(2) Å, c = 14.509(2) Å
α = 14.509(2)°, β = 96.320(2)°, γ = 90.278(2)°

Ratio:

a:b:c = 0.376 : 1 : 1.024

Comment:

space group P-1 to R = 6.64 %