[He hums thoughtfully.] I don't have any samples on me now, but... Let's see... [He starts noting with his fingers as he goes along.] Gold and silver, which are pretty common and don't have strong attributes themselves. Sapphire, ruby, star ruby, and green beryl, which I've used for weaponsmithing with Sokka. They can give elemental attributes -- sapphire has water, ruby and star ruby can have fire, and green beryl has wind.

There's also rarer ores and gems, but they're usually used for weapons or armor.