One of the most important early mineral finds was obsidian. Obsidian comes from the terrific heat beneath Earth’s crust.
It spews up in volcanoes as lava and hardens into volcanic glass. When shattered, obsidian separates into knife-edged flakes. These flakes can be as sharp as a razor.
Some of the earliest humans set and bound obsidian flakes into sticks of wood, making combination knife-saws. When treated with care and respect, these natural knives could be used for years.