The blue areas all belong to one crystal of enstatite that has been partly changed to talc as hot, water-rich solutions infiltrated the rock along fractures and cleavage planes. You can see the original outline of the enstatite crystal, marked by the dashed line in the diagram. The combination in this rock of enstatite, talc, phlogopite, and diopside, all magnesium-rich minerals, suggests that it was once part of a magnesium- rich salt deposit.

Crossed polarizers with gypsum plate