Additional Gems is a small mod in charge of adding new minerals to the game. Specifically, with this mod installed we can find up to six types of gems, which will appear in the basement of the world, as if they were of any other mineral resource.
Precious stones are amethyst, ruby, emerald, sapphire, topaz and crystal. With these new minerals we can create new sets of tools, weapons and pieces of armor. We can also make amulets, which will give us favorable side effects. All of these gems have a power similar to that of diamond, although they have a durability similar to that of iron.