The light colored background is a single crystal of diopside, a calcium-
rich pyroxene. The pools of brightly colored crystals are individual
plagioclase grains. The plagioclase grows through the pyroxene in a grid
pattern that resembles a wire screen or a sieve. This pattern is
controlled by cleavage planes in the pyroxene. Look for tiny bubbles inside
some of the plagioclase grains. These are places where fluid is trapped
inside the growing crystals.
Crossed polarizers with gypsum plate