I have stumbled upon another batch of my favorite type of rock - river-polished granite. So perfect but so slick. Boulder after boulder of wavy, bullet-hard goodness. The rock in this particular area has least amount of friction I have ever encountered. It feels slicker than glass. I lack the vocabulary to adequately describe it to other interested parties.
Mohs scale of mineral hardness is convenient shorthand for geologists to talk each other. Climbers need a similar scale for rock friction. I propose additional systems of letters to describe friction (or lack thereof). The rock described above would be type "A." Yosemite granite would be type "C." Southern sandstone would be type "F". Limestone with little spikes (name?) would be type "M."
