I've wandered around checking ores. My list mostly corresponds with Joram's. There are 17 gemstones, and 8 types of ore. Each ore seems to give out only two specific types of gemstones (which makes sense), and they are as follows:
Iron Ore: Amber, Diamond
Red Ore: Moonstone, Ruby
Droxerlite: Spinel, Opal
Black Rock: Obsidian, Pyrite
Fossil: Topaz, Sapphire
Venom Stone: Emerald, Tiger’s Eye
Malachite Ore: Malachite Gem, Aquamarine
Gold Ore: Quartz, Crystal
???: Pearl
Each ore has a level of commonality in the game.
Commonality:
Iron Ore: Very Common
Red Ore: Very Common
Venom Stone: Very Common
Droxerlite: Common
Black Rock: Rare
Gold Ore: Rare
Fossil: Extremely Rare
Malachite Ore: Extremely Rare
???: Pearl
