Minerals. Feldspar Minerals. Feldspar Minerals: group of silicates; mineral of crust, cleavage at 90 with flat, rectangular, glassy surfaces 1. Albite ( Plagioclase): Plagioclase Feldspar: calcium to sodium rich; example is albite ; has striations (thin parallel grooves)
What are the two most abundant elements by mass found in Earth's crust?
2. sodium and chlorine
3. calcium and carbon
4. oxygen and silicon