Appreciation post: I finally stopped calling every dark, heavy rock 'basalt'

For years I'd pick up a dense, fine-grained black rock and label it basalt in my collection. A trip to the geology lab at my local college showed me one was actually a hornfels, proven by a quick thin section under a scope. How many other common IDs are we all getting wrong out of habit?

2 comments

2 Comments

christopher49313h ago

My whole rock collection from high school is probably mislabeled. That thin section trick is a real eye opener.

keith94311h ago

Hold up, christopher493, I gotta push back on that. A good eye and a hand lens can get you really far for basic field ID. Not everyone has access to a petrographic scope, and a lot of those old labels are probably still right.