Fluorophlogopite in Burmese Spinel
Lotus Gemology in Bangkok received a large parcel of dark red spinels for identification. Their colors, inclusion features, and trace element chemistry suggested that they originated from Myanmar’s Mogok Stone Tract.
In one faceted specimen, a crystal was found breaking the surface (figure 1). The crystal’s surface luster suggested a refractive index below that of the host spinel, and undercutting suggested it was also significantly lower in hardness. The inclusion’s interior also displayed signs of cleavage (figure 2). Thinking it was possibly a carbonate, we proceeded to do micro-Raman analysis on the crystal. To our surprise, the result was fluorophlogopite.
Fluorophlogopite, KMg3(AlSi3O10)(F,OH)2, is a species in the mica group and a member of the trioctahedral mica subgroup. To the best of our knowledge, this is the first reported instance of this species in spinel. Nor are we aware of it having been found included in any gem mineral to date.