diatoms & scanning electron microscope with AAS, dats all u need

I've not seen a lot about the composition of phytoliths.  They can be decomposed for analysis in two ways. 

First, by solutions of HF in the presence of HCl, then xs boric acid is usually added to complex the fluoride as the acid stable fluoroborate ion. The solutions can be analysed by a combination of ICP techniques depending on your needs.

Second, they can be dissolved in molten alkaline fluxes such as Li borate and the melt poured into moulds for analysis by XRF.  These melts can later be dissolved and analysed for trace constituents using ICP-MS.

If you want to look at them intact the SEM is one way to go at very high resolution.  A lower resolution option is synchrotron radiation.

You might also consider laser ablation ICP-MS

You may want to contact Wendy Zellner at USDA-ARS Toledo. 

[email protected]

http://www.ars.usda.gov/pandp/people/people.htm?personid=48449

I have only just seen this, but we wrote quite a lot of papers on this topic if you are still interested. Essentially, we found that this was quite a common phenomenon in conifers when they were grown on acidic substrates.