acid

Hi What are these? And how did they get in the limestone I was dissolving in acid to release some kind of fossil that is in it? The Limestone is from north central Indiana. Here are some pics of the limestone specimen that these came from: I appreciate anything at all that I can find out...

I found some flakes is an area that I did not expect to find any traces of gold & I wanted to test it to see if it was real, so I dumped some hydrochloric acid on one of the flakes in a shot glass, waited a couple minutes, swirled it around a bit, waited about 10 minutes total, swirled some...