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Can anyone help identify this rock?

0 votes

A little background first. My brother works for a company that hosts a huge picnic every summer, and at this picnic they have a large booth every year where you "mine" for minerals - basically you get a big bag of dirt and you sift it out through running water and see what rough stones you get. Unfortunately, since everything is mixed, there is no way for me to know where the stones came from. But I have found some very nice stones - amethysts, rose quartz, snowflake obsidian, even a single piece of ruby-in-fuchsite. But this one I am at a complete loss to identify, and I hope someone can help me.

I'm sorry for the quality of the pictures, my camera isn't very good. The stone has many beautiful shades of orange, ranging from an orangy-brown on the darkest parts to a pretty light peach. The colors are arranged in bands along the edges, and the rough top shows different sections of orange, peach, and a tiny bit of white.

I'm not sure if it's a kind of jasper (most likely), or perhaps sardonyx? If anyone could help, I'd greatly appreciate it. I don't feel right adding it to my collection without trying to get an opinion on it.

asked May 23, 2016 by Lauren Kollett (120 points)

1 Answer

+1 vote

Lauren, what you have there is an agate. If you backlight it or hold it up to a light source like a light bulb or a flashlight, light will shine through it. It will have a translucent quality. You can see the different layers better that way. Agate is formed from a liquid solution of water with high concentrations of silica.. Micro crystalline Silica rich solution forms agate, chalcedony, chert, flint, opal, tiger eye and such. Macrocrystalinear silica forms the quartz you find at the beach, rosy Quartz, smoky Quartz and other such. The outer crust or matrix could be rhyolite, it is pinkish. Anyway, it is part Lake Superior agate. Agate can form inside of air pockets formed by volcanic rock. When cooling the bubbles are empty. Later, silica rich waters flow and evaporate leaving behind silica and trace minerals which can color the bands. Each time the air bubble fills and evaporates, another band is formed. For a rock to be considered an agate it must be 50 % agate. So that's why I said yours is part agate. Here's one like yours I backlit. Yours appears to be more weathered.

answered May 23, 2016 by Weasel (38,360 points)
Thank you very much! Mine is a rough stone, not polished. I held it up to a flashlight and it was not translucent, but thank you for giving me an answer!

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