Please forgive me, I'm completely green. I ran the GM1000 detector over what appears to be some crystallized rocks that were surrounded by basalt. The detector made a very weird echo sound & would start high & fade away. I've heard the typical siren sound it makes sometimes as if there's an error or too much iron around the target, but this sound is completely different & would only sound off like this in this tone over these crystallized rocks. I've only had this machine for a few weeks & it didn't come with much instruction. I don't really know what to search for as far as th