Preforms or finished tools?

I've done a lot of surface collecting of Native American artifacts over the years. One of my most exciting finds was on a friend's property in western Colorado. I was walking the area and found a lot of chips scattered about. I discovered two that were very similar in style within inches of each other. I scratched the surface where I found them and the result is the photo below. It was my first cache. These were all together in a 6" by 6" area. All of them are made from some form of chalcedony, "silicafied ash" and possibly petrified wood. There were no other chips or flakes, proving to me it was a cache of blades buried there on purpose. The only other artifacts I found at this site were a few broken projectile points, some scrappers, and a very nice knife. One very interesting piece I found at this site is a large piece of petrified wood that clearly shows knots and growth rings. It appears that an edge was used to hammer something. I wonder what they thought of this rock? I've found a few of these types of blades all over the country and often thought they were preforms. In some areas they're called "microblades". This cache aroused my suspicions and I performed an experiment.

The blades in the next picture are from a cobble of raw, red agate/chalcedony from Indian Springs, Nevada; it is not heat treated. To begin my experiment, I spalled these off and used all of them, as is, in various chores to see how they would hold up. I cut rawhide, carved and debarked wood, worked bone and antler, and cut meat with them. They were used for everything from heavy cutting to fine detail graving. There was very little change other than some polishing and micro edge flaking from use. They all stayed very sharp and did remarkably good work on the various tasks. I favored the large blade (bottom row, second from left). The top surface started to show a bit of polishing from handling and use. The only polish on the other blades are on the working edges.

The reason for this experiment was to prove to myself that the cache of genuine blades was not for future knapping but a group of tools to be used as is. I examined all of them. Several show signs of wear and polishing like the experimental ones; some had no wear at all. I believe these were both old and new tools buried together at the same time. Also, the shape and size of some of them negate their being made into anything else. There just isn't enough material to knap something further. As to size, the largest one in each photo is 3" long.