| Element | % |
| Oxide | % |
| k0412-1 |
| |
| |
| O | 42.76±0.18 | | | |
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2mm x 1.5mm x 1mm black prisms
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National Bureau of Standards
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| |
| Mg | 11.66±0.12 | | MgO | 19.33±0.20 |
| Al | 4.91±0.11 | | Al2O3 | 9.27±0.20 |
| Si | 21.20±0.09 | | SiO2 | 45.35±0.20 |
| Ca | 10.90±0.14 | | CaO | 15.25±0.20 |
| Fe | 7.74±0.16 | | FeO | 9.96±0.20 |
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| Sum | 99.2±0.3 | | Sum | 99.2±0.4 |
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