[Kunama]

There seems to be enormous conjecture about the the naturally occuring crystalline mineral 'Fluorite' or 'Fluorspar' which is in its laboratory grown version known as CaF2 or calcium fluoride.

Then the telescope optical world refers to it by its natural mineral form 'fluorite'.

The real confusion arises when people marketing scopes with objectives made of FK (fluoro-crown) glass and S-FPL glasses with some fluorine component latch onto the bandwagon of CaF2 and its wonderfully low dispersion properties to sell their scopes as 'Fluorite'.

Where are the "Dirt People" when we need them.

As far as I can see Takahashi F series (FS,FC,FCT) are the real deal using laboratory grown CaF2 supplied by Canon-Optron. As for the rest who knows

but

Ohara S-FPL53 and 51, FK61 et al are not CaF2.

Dirt people please chime in to confirm ..........