(% oxide)

B4 bulk

B7

B10

B12

SiO₂

64.38

69.24

69.12

70.08

Al₂O₃

14.55

14.11

13.92

13.91

Na₂O

5.79

5.77

5.21

5.37

K₂O

2.47

2.99

3.12

2.90

CaO

2.90

1.62

1.63

1.88

MgO

1.30

1.27

0.46

0.60

FeO

7.82

4.80

5.78

4.70

TiO₂

0.65

0.28

0.69

0.56

SO₃

0.03

nd

nd

nd

Cl₂O

0.11

nd

nd

nd

Ratio

SiO₂/Al₂O₃

4.42

4.94

5.0

5.0

SiO₂/FeO

8.23

16.10

12.0

14.9

SiO₂/CaO

22.20

42.74

42.4

22.7