Otto

Calcium fluoride does not exist in groundwater.  As this water flows over rocks it picks up fluoride ions leached from calcium fluoride and fluorosilicates in those rocks.  These fluoride ions are to what is commonly referred as being "naturally occurring" fluoride.  These ions are identical to those fluoride ions released into water during the fluoridation process.  A fluoride ion is a fluoride ion regardless of whether it is released from calcium fluoride, fluorosilicates, or any other compound.  This is elementary chemistry.

Steven D. Slott, DDS