Composition

Center edge

Na2O

0.05

0.03

0.05

FeO

30.49

31.83

31.92

K2O

0.03

0.02

0.03

SiO2

37.54

37.32

37.17

MnO

0.77

0.93

1.16

MgO

2.05

2.30

2.09

CaO

7.61

5.43

5.38

Al2O3

21.13

21.35

21.43

Total

99.71

99.19

99.28

Na

0.02

0.01

0.02

Fe

4.08

4.29

4.30

K

0.01

0.00

0.01

Si

6.01

6.01

5.99

Mn

0.10

0.13

0.16

Mg

0.49

0.55

0.50

Ca

1.31

0.94

0.93

Al

3.99

4.05

4.07

Total

16.02

15.97

16.02