Traditional stone arrowhead and knife making is accomplished by breaking the rock along natural “fault lines” in the rock, if you will. Certain types of rock have nice, parallel lines along which to break, and some don’t.
Obsidian is the classic material from which to make arrowheads. Obsidian flakes easily and predictably. Obsidian is volcanic glass. Man-made glass can also be used to make colorful arrowheads.
Flint, or its cousin, chert are also classic materials for arrowheads.
Other materials which Sam uses to make arrowheads and knives include: jasper and chalcedony. Sometimes he uses basalt, which is a very hard material.
People often ask if Sam can flake turquoise. In general, turquoise is too soft for flaking, and it doesn’t have the proper qualities of breaking. I’m avoiding the word flint knapping because Sam doesn’t like it. He prefers tsail haigath, an Apache term.

glass arrowhead