If you have a half bred horse say its 67% paint and you want to make it fullbred paint then you use the diamond horse shoe to make it 100% purebred.

They sell for anywhere between 700 - 1.5 million depending on demand.

You can either buy diamond horse shoes or find them around the game :)

p.s Items appear randomly on pages so if you see something click it could be worth something :D

Also some players use Diamond Horseshoes to add super lines and dna lines into their horses. For example you bought a rare breed on the game you need to boost up that rare breed so you crossbreed your rare pony to a different horse that say is a super horse with 8 or 9 positive dna. Once you do that your mare has its foal on either Thursday or Sunday depending on when you breed. Then you have a foal that is crossbreed so if it comes out the breed that you are looking for then you take that diamond hs and make it pure so you can add it into your lines when it is ready.