Calciomurmanite (original) (raw)

Formula:

(Na,◻)2Ca(Ti,Mg,Nb)4[Si2O7]2O2(OH,O)2(H2O)4

Colour:

pale brownish, purple

Name:

in allusion to calcium content and relation to murmanite

The Na-Ca ordered analogue of murmanite. Chemically related to, e.g., kolskyite.

One of many species based on sheet-structured HOH heteropolyhedral-octahedral blocks. It has three sheets of the following content:

- the O sheet: NaO6 and TiO6 octahedra forming alternating chains
- the H sheets: disilicate groups + TiO6 octahedra + CaO8 polyhedra

Water is located in 2 sites within the interlayer space.

Class (H-M):

1 - Pinacoidal

Cell Parameters:

a = 5.3470(6) Å, b = 7.0774(7) Å, c = 12.146(1) Å
α = 91.827(4)°, β = 107.527(4)°, γ = 90.155(4)°

Ratio:

a:b:c = 0.756 : 1 : 1.716

General Appearance of Type Material:

lamellar crystals, up to 0.1 × 0.4 × 0.6 cm, may form fan-shaped aggregates, up to 3.5 cm

Place of Conservation of Type Material:

Type material is deposited in the collections of the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow, Russia, catalogue number ST4994; cotype material is deposited in the collections of the Bel’kov Museum of Geology and Mineralogy, Kola

Geological Setting of Type Material:

hydrothermal in hyperagpaitic (peralkaline) rocks, resulting from low-temperature alteration (hydration + cation exchange) of a high-temperature phosphate-bearing titanosilicate precursor (possibly lomonosovite and/or beta-lomonosovite); associated minerals are those at the holotype locality (Flora Mt.)

Associated Minerals at Type Locality:

Reference:

Lykova, I. S., Pekov, I. V., Chukanov, N. V., Belakovskiy, D. I., Yapaskurt, V. O., Zubkova, N. V., ... & Giester, G. (2016). Calciomurmanite,(Na,□) 2Ca (Ti, Mg, Nb) 4 [Si2O7] 2O2 (OH, O) 2 (H2O) 4, a new mineral from the Lovozero and Khibiny alkaline complexes, Kola Peninsula, Russia. European Journal of Mineralogy, 28(4), 835-845.