Welcome Missbrooke! Pyrite is not heavy so I'm going with gold nugget. The other
reminds me of a story I read about the mines near Carson City Nevada. They were
digging along and found some gold but then ran into hard rock. The mining engineers
in the US at that time had little experience in mining in hard rock so they sent for
a mining engineer from the copper mines in Ireland. When the man arrived they
took him down to the mine and started asking him questions on how to extract
gold from hard rock. He was distracted by the huge pile of tailings nearby.
Standing there with his jaw agape he finally got the composure to tell the American
engineers that the huge pile of solid black tailings was nearly pure silver.