probably an M.C. Etcher can’t score deeply enough for a reliable snap — some folks have reported success under specific circumstances — a further caution is that the tool should not go past the edge which may damage the artificial diamond
if milled, likely best to do so in a water bath — note that the glass shards must be disposed safely and absolutely not poured down a drain (they will shred the filters of you local community water system)
See:
(there might be one or two more which could be found with a search)