I finally figured out how to tell chert from limestone in the field

I used to get them mixed up all the time, especially when they were both a light gray color. A geologist friend told me to just carry a small bottle of vinegar in my pack. Last week in the Ozarks, I tested a piece I thought was limestone, and it fizzed like crazy. The piece right next to it, which looked almost the same, did nothing. I mean, it's such a simple trick, but it saved me hours of second-guessing. Has anyone else got a good field test for telling apart similar-looking rocks?

3 comments

3 Comments

haydensanchez26d ago

Carrying vinegar just to check rocks seems like a lot of extra work. I get it if you're a professional geologist, but for most of us, is it really that important to know right away? They're just rocks. You could always just take a picture and look it up later when you get home. The whole thing feels a bit over the top for a casual hike.

the_xena26d ago

Honestly, that "just take a picture" idea sounds good in theory, but it never works for me. I get home and the photo looks totally different than real life, or I just forget to check. Tbh, having a quick test right there stops the wondering. I tried to figure out a slab in my backyard for weeks before I just bought a dropper bottle of acid. Ngl, seeing it fizz or not fizz is way more satisfying than staring at a blurry phone picture later.

kellyl322d ago

Yeah, the blurry phone picture method is a total trap... I once took like twenty photos of a weird rock, got home, and they all just looked like gray blobs. My phone's camera roll is basically a geology-themed abstract art gallery now.