Research Report: Natural and artificial black soils look different under UV light

by Richard L. Thornton, Architect & City Planner

Currently, I am analyzing various types of soils that we know for a fact were cultivated by Native Americans. I am seeing a difference between natural top soils and the contents of agricultural platform mounds. We need a sample of the soil in a terrace complex. It is illegal to dig soil from the terraces in archaeological zones, owned by the Federal Government.

These two samples were examined in a digital microscope at 1200X and illuminated with an Ultraviolet light. The darker colors are probably iron oxide or organic carbon. The mauve color is feldspar. The dull white color is either quartz crystals or calcite from bones and shells. The brightest whites came from fluoride in bones and shells.

A sample of man-made soil from an agricultural platform in Key West, Florida contained the brightest objects. Some were large enough to be clearly identified as bits of sea shells. There were also probably bits of animal bones in this platform. Evidently, sea shells contain more fluoride than animal and human bones.