Here's a map I've created, this is data I've collected from the past few days of mining, every Red dot represents a vein that has had a consistent spawn location in that area per restart. Even though these veins spawn randomly, this map should allow you to get a general idea to look in those areas with isolated tree islands. (green areas on the map)
Also quick mining facts.
- Rarity for each gem is the same, you have an equal chance to receive any of the gems in the list of the code. No gem is more rare than the other
- You can sometimes get 2 gems from a gold ore vein.
- There are rumored MassGraves_dze that spawns legendary loot.