Golden rocks obtained by training Construction are part of the Statue of Rhiannon. 2 are required each to complete the statue each week. Golden rocks may be stored inside a statue collection bag.
Obtaining
Making gold jewellery (best is to make gold bracelets); making items from leather or dragonhide; making molten glass in a furnace (as well as blowing it into glass objects); throwing clay on a potter's wheel (but not firing clay); making slayer rings; making cloth on the loom at a clan citadel; spinning items on a spinning wheel; crafting any type of battlestaff; blowing potion flasks; playing harps in Prifddinas. Crafting silver items will not yield golden rocks.
Creating crystal flasks or playing the harps in Ithell district during Voice of Seren will yield higher golden rock chances.