|
Oxide
|
Composition
(wt%) |
Element
|
Cations to 20 O
and 4 OH |
|
|
|---|---|---|---|---|---|
| 179-1105A-17R-1, 71-75 cm | |||||
| SiO2 | 36.2 | Si | 5.626 | Z | 7.957 |
| TiO2 | 3.53 | Ti | 0.413 | Y | 5.959 |
| Al2O3 | 12.72 | AlIV | 2.331 | X | 1.758 |
| FeO | 29.26 | Fe | 3.803 | O | 20 |
| MnO | 0.17 | Mn | 0.022 | OH | 4 |
| MgO | 7.43 | Mg | 1.721 | ||
| CaO | 0.01 | Ca | 0.002 | ||
| Na2O | 0.37 | Na | 0.112 | ||
| K2O | 8.29 | K | 1.644 | ||
| Total | 97.98 | Total | 15.674 | ||
Notes: Z, Y, and X refer to the ideal chemical formulas of biotite (X2Y6Z8O20OH4), where X = Na + K + Ca, Y = Ti + Fe + Mn + Mg, and Z = Si + Al. O = oxygen, OH = hydroxyl groups.