Mining picks can be purchased from the NPC Thane in Thane's Cave in the Wilderness at coordinates 185, 018.
Thane sells Mining picks for 200 coins each.
Mining picks are used for the Mining skill. They are utilized by first using a Mining pick to determine if something is there, and then by dropping the Mining pick and picking it up again. This will unearth a variety of items, such as Ore, Mica, Topaz, Amethyst, Quartz, Amber, and Diamond.