| Composition | Center edge | |||||||||
| Na2O | 0.06 | 0.00 | 0.04 | 0.07 | 0.08 | 0.03 | 0.06 | 0.00 | 0.03 | 0.02 |
| FeO | 28.50 | 28.86 | 29.49 | 30.48 | 30.82 | 31.92 | 32.27 | 31.57 | 32.71 | 33.58 |
| K2O | 0.00 | 0.01 | 0.00 | 0.00 | 0.01 | 0.00 | 0.01 | 0.00 | 0.00 | 0.02 |
| SiO2 | 37.07 | 37.23 | 37.03 | 37.07 | 36.23 | 36.92 | 36.91 | 37.17 | 36.83 | 38.07 |
| MnO | 5.98 | 5.89 | 5.34 | 5.01 | 3.95 | 4.00 | 3.22 | 2.71 | 1.69 | 1.58 |
| MgO | 1.32 | 1.28 | 1.40 | 1.45 | 1.45 | 1.60 | 1.58 | 1.77 | 2.01 | 2.09 |
| CaO | 4.78 | 4.75 | 4.52 | 4.14 | 5.14 | 3.62 | 4.11 | 4.56 | 4.46 | 3.91 |
| Al2O3 | 20.90 | 21.00 | 20.90 | 21.02 | 21.60 | 20.98 | 21.15 | 21.11 | 21.18 | 21.39 |
| Total | 98.61 | 99.10 | 98.73 | 99.26 | 99.40 | 99.08 | 99.37 | 98.90 | 98.94 | 100.64 |
| Na | 0.02 | 0.00 | 0.01 | 0.02 | 0.03 | 0.01 | 0.02 | 0.00 | 0.01 | 0.01 |
| Fe | 3.89 | 3.92 | 4.02 | 4.14 | 4.19 | 4.35 | 4.38 | 4.29 | 4.45 | 4.47 |
| K | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 | 0.00 |
| Si | 6.05 | 6.05 | 6.04 | 6.02 | 5.89 | 6.01 | 5.99 | 6.03 | 5.98 | 6.06 |
| Mn | 0.83 | 0.81 | 0.74 | 0.69 | 0.54 | 0.55 | 0.44 | 0.37 | 0.23 | 0.21 |
| Mg | 0.32 | 0.31 | 0.34 | 0.35 | 0.35 | 0.39 | 0.38 | 0.43 | 0.49 | 0.49 |
| Ca | 0.84 | 0.83 | 0.79 | 0.72 | 0.90 | 0.63 | 0.72 | 0.79 | 0.78 | 0.67 |
| Al | 4.02 | 4.02 | 4.02 | 4.03 | 4.14 | 4.03 | 4.05 | 4.04 | 4.06 | 4.02 |
| Total | 15.96 | 16.00 | 15.97 | 15.98 | 16.09 | 15.98 | 16.04 | 15.95 | 16.00 | 15.93 |