The Pyroclasts are perhaps the most unusual collection. Technically, they are too large to be considered "volcanic Lapilli". Generally, the pieces are a combination of lava-like volcanic glass (black and other colors) with stone, bone or metal fragments. They were collected by the survivors of each devestating eruption and then carved into the standard tool shapes. It's possible that pieces with bone fragments were highly prized. for their special powers.
On some pieces, the Paleo-Indians chipped the glass to create a twinkling eye or eyes. You can see this when you hold the piece at the proper angle or turn the piece around in the sunlight.
Some pyroclasts have shades of red, green, purple and yellow. These colors represent natural elements that were formed deep inside the Earth. When the eruptions occurred, they were carried upward by the superheated steam and the colors formed when they oxidized upon contact with the air at the surface.
These pieces are extremely rare because hydrothermal vents are usually asssociated with underwater volcanoes.