it's copper . lies in the ground for about 150 years. Put it in ordinary food vinegar for a week and you will see exactly this product. Scrub it afterwards with a brush, after the vinegar.It looks like a product in the form of pyramids round, and it was crushed from above.
such items are a sign that there must be coins from 1800. Necessarily. I did not meet places where copper and bronze lay in 1800 and there were no coins. Friend, look for more. Dig there more and all the colored signals without exception. There are coins within a radius of 100 meters.