If you are unsure if a rock is a disguised golem or not, a spyglass shows their name and level even when disguised. Also, when disguised, the rocks often move slightly as you get close, re settling onto the terrain.
If you kill them using a thyla’s gnashed ability then you can harvest their body with an anky. Killed a level 95 and just got 198 stone, 114 Crystal, 134 obsidian, 123 oil, and 78 metal from it. Hope this is useful to someone!! Have a nice day!!! :)
All rock elementals have the same rock skin when disguised. It is a bright yellow boulder and is very noticeable against dark mountains. Keep your distance, as they can aggro on to you when you get close.