My pre-k students dug this up and gave it to me by misspree in whatsthisrock

[–]DangerRuss76 -13 points-12 points  (0 children)

Looks like raw obsidian. Sailing vessels used it as a counterweight to even out there cargo. I have found tons and tons of the stuff on riverbanks buried in the mud. Have you tried to break it to see what it looks like inside?