Plagioclase

Large sample of white twinned crystals of Plagioclase with a vitreous lustre and perfect cleavage. Plagioclase has a sodium end-member (Albite- NaAlSi3O8) and calcium end-member (Anorthite-CaAl2Si2O8). Colour can be white, colourless, grey, green, bluish, reddish, a play of colours (Albite and Labradorite), blue, green, yellow or red. Lustre is vitreous but is usually pearly on the cleavage. Streak is white and hardness is 6. Cleavage is good in two directions at nearly right angles but poor in a third direction. Twinning striations are very common on cleavage planes and cleavage is frequently curved. Plagioclase can be thin blades (Albite) in matrix or it can be found as lamellar, granular, disseminated or rosettes. Plagioclase can also be twin crystals that resemble platy crystals sandwich together.