All of the original cells are replaced one by one with minerals, often a silicate such as quartz, leaving the original cell structure intact. And while there is often amazing preservation of the big woody bits, the telltale leaves that help us identify that wood to species are often lost. If this is the case, we add our best guess at the genus and add xlon. So, Palmoxylon is the indeterminate wood of a palm, though we may never know which palm. If you have an interest in botany and fossils, you may want to consider making a career of it. The study of fossil wood is called palaeoxylology, with a palaeoxylologist being someone who studies fossil wood. Pretty cool, eh!