Leaching of Fluoride from Biotite Mica in Soil: Implications for Fluoride in Shallow Groundwater

Table 2

Major and minor element composition of two representative fresh biotite samples and average chemical composition [22]; LOI: lost on ignition, n.d: not detected.

Element oxide wt%	SL 23	SL 26	Average (𝑛=8)
SiO2	45.43	44.12	44.35
Al2O3	34.86	33.95	34.56
Fe2O3	1.81	1.78	1.73
MnO	0.01	0.02	0.01
MgO	0.69	0.76	0.81
CaO	n.d	n.d	—
Na2O	0.70	0.70	0.35
K2O	10.22	9.98	9.87
TiO2	0.37	0.36	0.35
P2O5	0.03	0.78	0.43
LOI	4.82	6.28	5.98