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Spent a whole weekend trying to tell two granites apart
Had a rock from a job site near Boulder. Thought it was a common granite. Looked at it under my loupe, checked the grain. Everything said granite. But the color was a bit off, more pink. Figured it was just a local thing. Tried to match it in my old field guide for three hours. Nothing. Finally took a thin section to a friend with a real scope. Turns out it's a specific type called Pikes Peak granite, with a lot of pink feldspar. The whole thing took me from Saturday morning until Sunday night to sort out. Just a simple rock ID turned into a two day project. Anyone else get stuck on a simple ID that turned into a deep dive?
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terry_martinez13d ago
Been there with the pink feldspar throwing everything off. A small acid bottle in your kit can save a lot of time for those tricky silicates. Spencer_ellis is right about chert fooling a hardness test too, it's a real headache. Sometimes you just have to step back and check the most basic things again.
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spencer_ellis26d ago
Pikes Peak granite will do that. That pink feldspar is a real curveball if you are used to the grays. I had a similar thing with a piece of quartzite from the UP. Looked totally normal until I checked the hardness. Scratched glass just fine, but then it wouldn't scratch a steel nail. Spent a full day thinking my tools were wrong. Turned out to be a really dense chert that fooled me. Sometimes the simple ones eat up the most time. You just have to laugh about it later.
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