Hi DesuDeus, check here for some gemstone sources:
http://moi3d.com/forum/index.php?webtag=MOI&msg=3782.1


You may find some 3DMs with gemstones in them that only contain mesh objects saved from Rhino into the 3DM - if you encounter a 3DM that does not appear to open with anything in MoI you've probably run into one of those. You can probably still make use of those in C4D by using Rhino or that rhino.io plug-in to read the mesh data in C4D from the mesh 3DM file.

But I think there were some sources of NURBS gemstone models mentioned there too. (Jesse's collection here: http://moi3d.com/forum/index.php?webtag=MOI&msg=3402.4)

- Michael