i will write a better tutorail but basic way i do it is this.
Create base model
Decimate model to around 300k poly
Duplicate model
Zremesh model to around 5-10 k poly
export both models in OBJ format to matrix
import models one at a time into matrix
put the models on seprate layers
convert the low poly version to nurbs with command meshtonurb
select created nurb model, put on its own layer
use that version with gemstones on surface
proceed as normal