There is usually some OH in the F sites, however, and Fe and Ti can substitute for Mg, so the formula for the naturally occurring mineral is better written (Mg,Fe,Ti) 5 (SiO4) 2 (F,OH,O) 2.
ແຕ່ມັກຈະມີ OH ໃນສະຖານທີ່ F, ແຕ່ Fe ແລະ Ti ສາມາດທົດແທນ Mg ດັ່ງນັ້ນສູດສໍາລັບແຮ່ທໍາມະຊາດທີ່ເກີດຂຶ້ນຕາມທໍາມະຊາດແມ່ນຂຽນດີກວ່າ (Mg, Fe, Ti) 5 (SiO4) 2 (F, OH, O) 2