Although I love geoscience, I’m not a geologist, though I tried to become one. Mineralogy lab was tough – you had to identify rocks without using labels.
Sadly, YouTube and the Geology Kitchen weren’t around yet.
It’s even worse out in the field, of course. The Mohs hardness scale was a lifesaver. Where did it get that name? From its inventor, who expanded on earlier Classical work by Theophrastus and Pliny the Elder, per Dr. Wikipedia.
Here is Mohs in less than a minute:
Here is a slightly more in-depth biography. And this is his legacy to the world:
Featured image: Memorial plaque in Vienna, by Doris Antony, CC BY-SA 4.0, via Wikimedia.