We found quite a few groundstone artifacts on our survey. Above you can see a mano (hand stone) and metate (grinding slab) found on the surface next to each other. The Kamia who lived in the area in late Prehistory, were opportunistic farmers who grew maize and beans and used the manos and metates to grind corn meal.
If you look closely at this fine slab metate you can see the pecking scars that were used to shape it and to "sharpen" it after use. The glassy-smooth ground surface of the metate would have to be roughened periodically to more efficiently grind corn.
This last find really surprised us. You see me in the picture above holding a large pestle. It's very heavy and made of granite that must come from the mountains twenty miles or more west of where we found it on the desert floor.
Stone mortars and pestles are representative of acorn processing technology that is very common in the non-desert portions of California. The Kumeyaay who lived in the mountains where this pestle came from, processed acorns from the oaks that grew there, and traded the meal for maize with the Kamia who lived down here in the desert and had no oaks of their own.
This pestle would have been pretty useless where we found it. It was found all by itself, no other artifacts or features in association. As heavy as it is and as far as it had been carried, you can just imagine someone on a hot day a few hundred years ago dropping it and saying, "I not carrying this thing another step!"