I was wondering the same thing. It has a high mass fraction of both silicon and oxygen both of which are common substances in the crust and mantle. Yea, it was a bad joke especially considering mud is not homogenous (and the way they parenthetically entered "mudd" made it seem like they thought the compound given was a formula--per say--for mud) and, what's worse, clinochlore isn't even that abundant (my educated guess)

.
Also, it's not a phyllosilicate. Phyllosilicate's have a 2:5 ratio of Si:O in the silicon oxide group. I'm not quite sure how to classify it (I only know IUPAC which applies for organic not inorganic compounds. sorry! :P )