This specimen hosts one of the sharpest single crystals I have ever seen of the species, just razor sharp and equant, not rounded as usual. The crystal, to about 1 cm on edge, sits nestled in a well-trimmed and contrasting marble matrix. This is classic material now, best of species even. But, most are larger crystals on larger rocks and I cannot recall seeing a thumbnail-sized example that so grabbed me, as this one does, for its geometric form and intense, uniform-blue, color.