Since my spring fieldwork in Jordan I have spent a lot of time in the laboratory processing sediment samples for extracting microscopic silica phytolith remains which form in and around plant cells. These silica phytolith preserve very well in archaeological sediments and can survive for thousands of years.
The laboratory extraction involves a series of steps which are conducted over four to five days.
Sediments are sub-sampled from the original sediment, sieved to remove large particles and then carbonates are removed using a weak hydrochloric acid. The samples then undergo clay removal and then removal of organics by burning at 500 degrees Celsius. Phytoliths are finally extracted from the remaining particles using a heavy liquid at a specific gravity of 2.3.
The phytoliths are then mounted onto a microscope slide before being viewed under a cross polarising stereo binocular microscope at x400 magnification. The phytolith types are identified, counted and quantified for each sample.