Shiny black crystals of cassiterite, to 1.5 cm across, are associated with pearlescent muscovite which is nestled in the spaces between cassiterite crystals. Cassiterite is incredibly rare from the Mogok area. This is surely one of the finest examples and is in any case, the only good one that I have seen for sale. From the Burma collection of "Burma Bill" Larson, who has for decades brought out gems and then minerals as this region opened up to the trade in specimens.