Archaeology soil description

This pen is very useful for an archaeologist on an archaeological fieldwork to remember that when writing down your documentation, you have to actually describe the soil. Of course, after some hours (or days... or weeks...) of hard work, the temptation of describing the new layer as "f***ing dirt" grows... and that's why you need this pen! Or you are the tutor or teacher in an archaeology field school and you want to remind your students, in a funny way, that they have a job to do. This may make your job easier.