Chris etching a piece of specimen gold only makes sense if the gold is all interconnected into one piece in the rock. Check for electrical continuity between different areas of gold exposed on the surface to see if you get a clean signal. Etching away the rock when the gold isn't interconnected will just leave you with a pile of gold dust. There are much easier and safer ways to reduce the rock to dust than using HF.
I'm not going to make a judgement just from a picture but there doesn't appear to be any gold in the rock in your picture. The continuity test will help you determine if the rock has any metal in it. Gold conducts electricity very well, dry rock does not.
Good Luck and please be safe.