Mining

Either Mining Master or Mining Master Lee, in Serene City, will teach you Mining. But only Mining Master Lee will give you the training quest.

Ores
Ores are turned into ingots and these are mainly used by melee classes. Ingots are the main ingredients in Blacksmithing; and a minor ingredient in melee-class armour crafting and jewelry making.

Crystal Rocks
Crystal Rocks are used to craft jewelries with a level 1 Jeweler skill. Mining Crystal Stones for Crystal Rocks does not require a Hoe equipped. Having one equipped while mining Crystal Stones does not reduce its durability.

Crystal Rocks can also be mined in Monster Cave.