Reported by Zygus42 via CurseForge:

I was just testing (MC 1.10.2) and in chests in minecarts in an abandoned mine, every single cart had 6 or 7 of the new gem types in it (Indicolite, Moonstones, etc) - is this intentional ? seems a very high rate and no setings in the config to cover it .

Check net.silentchaos512.loot.LootHandler for issues.

Have done more testing since, and this hasn't happened again - not sure why. Bad RNG maybe ?