Board Thread:Questions and Answers/@comment-72.219.161.141-20121224175131/@comment-84.105.173.92-20121225114706

Those orbs are the stone and ores you just mined, just condensed in a neat little orb. When you pick them up you get the stone and ores back in you inventory. So you don't get the black orbs themselves, but the stuff you just mined.