(a) Blue hexagonal crystal of laurentthomasite in partially weathered pegmatite mainly composed of quartz, orthoclase, phenakite and secondary apatite. (b) Enlargement of (a). — Photo: Ferraris, C., Pignatelli, I., Cámara, F., Parodi, G., Pont, S., Schreyer, M., and Wei, F. · CC BY 4.0
Laurentthomasite
Laurentthomasite is an IMA-recognized mineral species in the silicate class, with the chemical formula Mg₂K(Be₂Al)Si₁₂O₃₀.
It crystallizes in the hexagonal crystal system (space group P6/mcc). It is a member of the Milarite structural group.
Key properties: Mohs hardness 6; specific gravity 2.67; Light blue streak; Vitreous luster; optically uniaxial.
IMA symbol Ltm, IMA status: approved, named in 2019.
Found in quartz-syenite pegmatites in a series of biotite- and amphibole-rich gneisses, migmatites, and pyroxene-rich alkali syenites.
It is found associated with Orthoclase, quartz, apatite, phenakite, beryl, albite, magnetite, thortveitite, cheralite.
The mineral was named to honor Laurent Thomas (b. 1971), French geologist, prospector, and mineral dealer since the early 1990s, especially for African areas such as Madagascar.