c/geology-rocks

A guy at a rock show in Tucson told me his granite countertop was 'just a rock' and it made me think

I think the obsession with finding 'perfect' quartz crystals is missing the point

Last week I was hiking near the old quarry in Barre, Vermont, and I saw a guy get really upset because a crystal cluster he found had some iron staining. He tossed it back. I spent the whole afternoon picking up 'flawed' rocks he and others had passed by. The story they tell, with the fractures and the mineral inclusions, is way more interesting to me than a clear, perfect point. Has anyone else found a 'messy' rock that turned out to be your favorite?

My cousin found a piece of granite in our backyard and said it was just a boring gray rock, but I showed her the pink feldspar crystals under my loupe.

She stared at it for a full minute in my garage and whispered, 'It's like a tiny, frozen galaxy,' which made me realize showing someone the small details can change their whole view.

I took a geology field trip to the Oregon coast and the difference between a guidebook and a real person was huge

I spent a day last fall trying to use a popular field guide to identify the basalt formations near Yachats. The book had nice pictures, but I kept getting stuck on the fine details (like the specific type of columnar jointing). Then I went back a week later with a retired professor from the local community college. In about twenty minutes, he pointed out the subtle flow banding and vesicle patterns that the book just glossed over. Having someone who could answer my dumb questions on the spot made everything click in a way that reading never could. Has anyone else had a learning moment that just wouldn't have happened from a book or a video?

Had to pick between a 4-inch and a 6-inch core barrel for a sandstone sample in central Utah. Went with the 4-inch.

Serious question, is it just me or are more people skipping the acid test for calcite?

I was at the mineral show in Tucson last month and a vendor sold a piece of 'selenite' that fizzed when I checked it at home. Has anyone else run into this, or am I being too careful?

Remember when we just labeled rocks with a piece of masking tape?

Switching to proper acid-free labels and a real catalog system saved my whole collection after a basement flood last spring. What's the best way you've found to keep track of everything?

Back in college, I would just grab any rock from a creek for my collection...

Now I spend a good hour looking at the layers in the bank first, ever since a trip to the Potomac River last fall. Seeing the clear contact between the graywacke and the shale made me realize the story is in the spot you pick it from. How do you guys decide where to collect a sample?

Just found out the basalt columns at Giant's Causeway formed in about 3 days, not thousands of years. Read it in a paper from Trinity College Dublin.

PSA: I just read that the pressure inside the Earth's core is over 360 million times the air pressure at sea level, which is a fact that absolutely blew my mind.

I found this in a geology textbook from the local library, and it makes our surface rock collecting seem like we're just scratching the planet's surface, doesn't it?

I used to think all those shiny black rocks on the beach were coal

I mean, I collected a bunch on the Oregon coast last summer thinking I had a cool haul. A geology student at the local visitor center told me they're actually basalt, and that coal is way less dense and would leave a mark. Has anyone else made this mix-up?

Vent: My vinegar test on a rock from Lake Superior backfired

I picked up this grayish rock near Marquette, Michigan thinking it might be limestone. When I put a drop of white vinegar on it, there was zero fizz, but the spot turned a weird orange color overnight. Turns out it's a piece of banded iron formation, and the acid reacted with the iron oxides. Anyone know a better way to test for iron content without messing up the sample?

Just found out some of the oldest rocks on Earth are in northern Canada

Honestly, I read it in a library book and it said they're over 4 billion years old. Has anyone been up there to see them?

Showerthought: I was calling all the dark, heavy rocks in my creek 'basalt' for years

A guy at the mineral show in Flagstaff pointed out my 'basalt' sample was full of olivine crystals, so it's actually peridotite. Anyone know a good field guide for basic igneous ID?

Bought a 'rare' thunder egg online and it was just a painted river rock

Spent $75 on what the seller said was a top grade Oregon thunder egg. It arrived looking way too perfect, like a shiny brown egg. I took it to the local rock club meeting and one guy just laughed and said it was a smooth stone from a craft store with spray paint on it. I tried to scratch it with a steel nail and the color came right off. Anyone know a good way to spot fakes before you buy?

My friend in Flagstaff said my rock labeling was 'chaotic neutral'

I used to just write the location and date on my samples with any pen I had (you know, like a grocery list). She looked at my box from a trip to the Grand Canyon and said, 'This says 'red rock, Tuesday'... that could be anywhere in Arizona.' Now I use a waterproof marker and put the exact GPS coordinates and rock type on every tag. Has anyone else had a labeling system that was, well, too simple?

Found a chunk of what I thought was obsidian in a creek bed near Bend

I mean, it was black and glassy, so I was sure. Took it to a local rock club meeting and a guy pointed out the conchoidal fractures were way too big and grainy. It was actually slag glass from an old smelting operation, which makes sense given the area's history. He showed me under a 10x loupe and the tiny bubbles were a dead giveaway. Anyone else run into industrial slag masquerading as cool volcanic rock?

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?

Saw the basalt columns at Giant's Causeway and the tourist info is wrong

The signs all say they formed from lava cooling fast, but the jointing pattern shows a much slower rate. Anyone have a good source on columnar jointing speeds?

Saw a cliff face near Sedona that looks totally different now

Honestly, I was there about three years ago and went back last weekend, and a huge section of the red sandstone has just crumbled away. Ngl, it looks like a recent rockfall after some heavy winter rains. Has anyone else seen a landscape change that fast from normal erosion?

My rock hammer gave me a choice: break the rock or break my thumb

I was out near Sedona last weekend trying to get a fresh look at a really nice piece of jasper in a basalt flow. The thing was wedged in tight, and I had to decide: give it one more solid whack with my Estwing, or try to pry it out with a chisel. I went for the whack. The jasper popped free, but the hammer bounced right off and smashed my thumb. I spent the next 20 minutes with my hand in a cold stream. Got a great sample, but my thumb is still purple. Anyone have a better method for stubborn rocks in hard matrix?

I was hiking near Sedona and saw a whole cliff face that looked like a stack of pancakes.

The layers were so perfectly flat and even, it made me wonder what kind of ancient event could have left sediment that neat, and if anyone else has seen formations like that around there.

I bought a cheap rock tumbler from a big box store and it was a total waste

Spent about $80 on a basic model from Harbor Freight last year, hoping to polish some local agates. The motor burned out after maybe 30 hours of total use, and the plastic barrels cracked. Ended up with a bin of half-polished, scratched-up rocks. Has anyone had good luck with a specific brand that can handle harder stones?

Had to pick between a rock saw and a tile saw for cutting my own slabs

I was trying to cut some agate I found near Tucson last month and my old tile saw just wasn't cutting it, literally. I had about $200 to spend and had to choose between a used lapidary saw from a local guy or a brand new wet tile saw from the hardware store. I went with the lapidary saw because it had a thinner blade and a slower speed. It took me a full afternoon to get it set up and aligned, but the first slab came out way cleaner with almost no chipping. Anyone have a good tip for keeping the blade from loading up with rock dust so fast?

Vent: I tried using a potato to clean a really stubborn calcite sample

I was cleaning a big calcite cluster from a dig in Kentucky, and it had this awful, greasy clay stain stuck in all the cracks. Nothing was working, not even a soft brush and soapy water. I remembered my grandpa saying something about using a potato to clean old coins, so I figured, why not? I cut a raw potato in half, rubbed the wet side all over the calcite, and let it sit for about ten minutes. When I rinsed it off, most of that nasty stain just washed away. I think the oxalic acid in the potato juice did the trick. It felt pretty silly, standing there rubbing a rock with a potato, but it actually worked. Has anyone else ever used a weird kitchen item to clean a mineral find?