What is the geologic origin of Cryolite, and could there be more?
Ivigtut Cryolite deposit, Ivittuut (Ivigtut), Arsuk Fjord, Sermersooq, Greenland deposit  is the first and largest occurrence of Cryolite but it is not the only location to report Cryolite.  

Some of these other locations listed below have produced collectible specimens but cryolite does not occur in large enough quantities to be mined. 

Other important locations are: Reference
(I have seen specimens from these locations)


ST PETERS DOME PEGMATITE PROSPECT, Pikes Peak Colorado    
Francon Quarry Mt St Hilaire, QUEBEC   


(other listed locations, Reference)


MONZONITE GROUP, Gunnison County Colorado
FANNY GOUGE MINE, Yancey Co. North Carolina
BARINGER HILL MINE, Llano, Texas
MC GUIRE PIT Marathon Wisconsin.   
Also reported from near Miass, Russia.


I also suspect there are other Canadian locations but Canada publishes less mineral data than the United States does. 

Cryolite occurs in syenite vein deposits (igneous rock which is quartz deficient) which had abundant amounts of fluorine.   

There are 13 other known mineral specimens that contain primarily: Na, Al, F. 
Cryolite is the most common mineral, due entirely to the Ivigtut deposit.
The geologic conditions at the Ivigtut deposit led to deposition of cryolite instead of an other mineral phase containing  Na, Al, and F.  

I believe additional deposits with cryolite may be found in the future but the Greenland deposit is likely to remain the first and most important deposit.
There are a handful of completely unique ore deposits on earth, Ivigtut Cryolite deposit is one of them.

See zincite from Franklin New Jersey as another example where a specific mineral was only ever commerically mined from a singular location.