Component

Percent by weight

Component

Percent by weight

SiO₂

38 - 46

Fe₂O₃

6 - 13

Al₂O₃

10 - 16

TiO₂

1 - 3

MgO

16 - 35

H₂O

8 - 16

CaO

1 - 5

Other

0.2 - 1.2

K₂O

1 - 6