Ores are a decent source of money, as they are usually obtained through questing (most quests will offer "xxx in gold and ores"), salary, mining, or random drops, and can be given to pets to sell. They are placed between chests and small medals in your inventory, and encompass the "raw ore of (diamond, mica, etc.)", stones/crystals, and junk stone. Unfortunately, you must identify each ore at least once before you are given a fair price for that type of ore.
Also, gold bars and raw ores of precious gems (diamond, emerald, etc.) can also be dropped on the floor of Your Home to increase it's rank, but the higher the rank of your house the more expensive they have to be to be counted. Note that only gold bars and ores in the top 10 furniture items will contribute to your House Rank. See your house board to view the top 10.
These are also the only items your pets are known to sell apart from small medals, and will usually make a killing doing so; when sold by pets, they will always receive a flat price depending on what they sell, from 10 gold for junk stone, to 450 for raw ores.
The entire class of "ores" are also preferred offerings for Opatos of Earth and Jure of Healing.
The ore pieces you find in the Wilderness are NOT considered ores, most likely being useless refuse from actual ore.