The Comet Shard (すいせいのかけら, Comet Shard?) is a valuable item that was introduced in Generation V. It has no side-effect except for to be sold.
In Generation V, it can be sold to the billionaire for 
60,000; in Generation VI, it can be sold at Poké Marts for 15,000; while in Generation VII, it can be sold for 30,000.