P3D Flourite lenses

[Rod Sage <rsage@xxxxxxxxxxxxxxxxxxxx>]

>  "The color aberration curve of a doublet can be made considerably flatter
>     by using special glasses or fluorite.

I believe most hard contact lenses are made from fluorite. I always assumed the fluorite made them semi-permiable but maybe it was because the fluorite gave the lenses a higher refraction index so that thinner lenses could be used, or  is it to correct color aberration.
RDS