This Stones should be placed in Events as a Redeem Item but nope .. Just like this last Mobilization, where they put the Purple Stones (Forgot the name) in the Redeem Shop of the Mobilization even tho we can get easily get it for free thru Group Shop for only 350 points per piece ..

Hope we see this Breakthrough Stones in some Events, as a part of the rewards or one of the redeemable items ..