Any armor with a Purity rating on it, will use the effects of the powersource. The amount of Purity is a Percentage of the max effects of the powersource.
Slot 13 aug slots, are for Purity improvement augs for armor. So if your basic armor piece has a Purity 50, and you add a Purity 25 slot 13 aug to it, you'll get Purity 75, or 75% of the effects of the powersource for that piece of armor.
Powersources come in all sorts of types, and from variuos places. There are player made ones, ones you can buy from Katta merchants, some with Orum, some with Phosephites and/or Phosphenes. There may be some purchasable in SoF and SoD zones with the appropriate faction and/or alternate currency.
Purity augs, are also purchasable in Katta, and one in particular is questable in Loping Plains, and that quested one, is 25, and is the only one I know of that won't be destroyed on removing it, with the appropriate solvent.
You'll have to look up the individual powersources to see benefits, detriments they have, from people's posts. Whichever powersource you equip, each purity tagged item you are wearing will recieves the purity percentage of the max powersource stat modifications.
Someone else may be able to give more information, on the SoF / SoD sources .. I just use Katta most of the time, since they have some good ones that are cheap.
Yther Ore.