What exactly is flint and where does it come from?  Anyone who has found or seen an Indian arrowhead has wondered this.  If you want to be scientific about it, then flint is a type of rock that is chemically composed of silicon dioxide.  All right, for us non-scientists, here is a more understandable definition.  Flint, used by stone-age people like American Indians to make stone knives, tools and weapons, is any form of stone that is comprised primarily of silica which has a property called conchoidal fracture.  WHAT?  O.K., this just means that it fractures in a rather uniform, predictable way.  That’s important when you are trying to make precise forms out of solid rock,...