Sourceshards drop from small bosses, these rare quality items look to be common from defeating ultimate boss of a Rift. You can use Rift Platinum (EU) to help you beat tough boss. Sourcestones are epic quality items and you can only gain them from large bosses drop. Through the ultimate boss, I am talking about the certain foe which spawns after finishing whole the targets of an invasion. I have just gained sourcestones while slaying the ultimate large boss in invasion events. When you are doing invasions, you should try to search for the ultimate boss once he spawns, and race over to the proper position then you will have your participation up other gamers complete the boss. Events are not always same, for some events where you only beat some invasions and an boss spawns, in general you gain a sourceshard and you will need Rift Plat (EU). For other events with some waves, generally you gain the sourcestone.
Sourcestones and soureshards a tiered, so you will gain a various sourceshard type off of lvl 15 foes, as you result you will off of lvl 25 foes. these items have multiple tiers, you can wield the rewards of high quality for different items and you can directly buy Rift Platinum (EU). For instance, you are able to exchange fifteen sourceshards of higher end in city for potent lesser planar essences, and equip then to your planar to get decent stat increases.