Dammit I should know this.

[reynardo]

There's a mineral, light-brown-yellow-and-white, that can be made into fairly sharp stone knife blades. They're using one of these knives in Pirates of the Caribbean to get the blood, and I'm sure I've seen them in other human sacrifice type movies. Not to mention rituals, earthing, circle-drawings, etc.

Any ideas? panacea? ambitious_wench?