I am actually in the geosciences using geohashes -
https://en.wikipedia.org/wiki/Geohash which are 64 bit integers. I
would like to store these geohashes in memory and then do range scans.

I want to be able to do range queries with geohash ranges and these
should be very fast.
As an example if I have latitude and longitude = 61.5,N 172 E
and another latitude and longitude = 61.4. 172.1 E both of these will
geohash to similar values with a similar prefix. We can calculate the
prefix with an lower and upper bound and retrieve all the geohashes in
that range. Is it possible with your implementation of ART ?

I do not see an API for range queries.