Carletonite

Carletonite is a rare silicate mineral with formula KNa₄Ca₄(CO₃)₄Si₈O₁₈(F,OH)·(H₂O).

It is a phyllosilicate and a member of the apophyllite group. Its tetragonal crystals are a translucent blue, white, colorless or pink with a vitreous to dull lustre. It has a density of 2.45 and a hardness of 4-4.5.