Geologists? I shit 'em...
To be fair not a lot of people know about silcretes (or their cousins calcretes). They tend to be fairly localised and are quite rare globally. I only know that cos I did my uni disertation on 'The Sarsen Stones of the Marlborough Downs' (mainly as an excuse to hang around Avebury for two weeks, but also cos I knew my lecturers knew nought of the subject!)