FELDSPAR

noun

14 Scrabble

16 WWF

F 4

E 1

L 1

D 2

S 1

P 3

A 1

R 1

Definition

Any of a large group of rock-forming minerals that, together, make up about 60% of the earth's outer crust. The feldspars are all aluminum silicates of the alkali metals sodium, potassium, calcium and barium. Feldspars are the principal constituents of igneous and plutonic rocks.