Potassium feldspar is a member of the feldsparmineral family. Like Plagioclase Feldspar, potassium feldspars are silicateminerals that contain a considerable amount of potassium. Feldspar crystals are stubby prisms, often pink to white. Some potassium feldspars, such as the one shown to the left have a streaky appearance (see closeup) called perthitic texture.[1]