This has been in the family for years. We would like some ideas on identity. Please help. Here is what I know. Hardness is probably 6-7. It took force from a wood screw to leave a scratch.
check the thinnest edge and see if backlight makes it translucent, interlocking fibers at microscopic level will be a dead giveaway. This character also makes it extremely tough to fracture with tools. Nephrite hardness 6.5
Obsidian is glass. Obsidian is not hard enough to strike a spark. I've seen green obsidian, and it wasn't near as pretty as what
you are showing. I don't think it's obsidian, other than that, I don't know what it is, except it's darn sure pretty.