Golden rocks obtained by training Summoning are part of the Statue of Rhiannon. Two are required each to complete the statue each time that it is built. Golden rocks may be stored inside a statue collection bag.
Creating summoning pouches. Unlike other rocks, the chance of a rock is given per pouch and not per action.
For best chances of obtaining the rock per pouch made, it is best to create pouches at the Amlodd obelisk during Voice of Seren.