With the recent update mining has gotten a slight overhaul. Gems are now hidden inside Gem Boxes (we have up to 4 different gem lootboxes) and come from the stone & andesite drop tables. Stone includes: Chiseled, Cobblestone, Stone and Gem boxes. Andesite includes: Granite, Diorite, Andesite, and Gem boxes. Other blocks are: Gold Ore and Iron Ore are aesthetic and drops the same as stone/andesite, Coal (Coal & Salt Chunks). You can use any type of pickaxe here successfully.

Types of Gem Loot Boxes

How to Clean Loot boxes from the Mine.

Drop Table Cobblestone, Dirty Pebble, Dirty Stone, Dirty Geode, Dirty Cluster. Dirty Pebble contains: Gemstones, Ores, and Basic Stone Building materials such as: andesite, granite, diorite, etc 

Gems Available