The upper mesh is made of goretex. The rest of it is genuine leather of course. These aren't really made for desert deployment, more jungle if anything. The goretex version is generally regarded to be the more comfortable sibling, with the mesh aiding flexibility and air flow.
There's another version without the mesh. Here's what they look like (well worn).
I've got a brand new pair of the meshed ones stashed away all ready to wear with a pair of bootcuts, alas i'm from one of those countries where just about every male citizen is/was a soldier, and wearing them out looks reallyyy tacky. Those boots shall have to wait a year then, til I relocate to the rolling hills of Massachusetts