Found this cool rock at lake Tahoe. It has 2 white rings around it that are so perfect I thought at first they were drawn. Now it lives in my Chia pet garden. Here's an additional pic.
this post was submitted on 30 Dec 2025
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Cool Rocks
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A place for:
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Be gneiss to each other.
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The cracks in the basalt weren’t parallel. They filled in at the same time. They weren’t (probably) horizontal. Much later, after it was filled in, it was broken again. Then water (river or ocean) smoothed it to be round.
edit: They’re not rings, they’re through the whole rock in a plane. “Layers” isn’t right either. The filled in part wasn’t horizontal when deposited. The quartz crystals grew in the cracks whichever orientation they were. So the single stone you have is really three basalt pieces stuck together with quartz “glue”
I did find this on the shore but it was lake Tahoe at around 7,000ft elevation. Could it still be from the ocean in that case? You guys seem to know what you're talking about and it's terribly interesting. I always just thought, "cool rock" but I love hearing all these theories.
Could be from one of the streams leading into the lake. Could be many, many years of the small but present waves of the lake hitting the shore. Or could have been created when the Sierra Nevada were closer to sea level.
Nice. Tahoe gets huge waves from time to time. Most of my cool rocks come from that area.
Waves were my top theory.