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Wed 22 Mar, 2017 03:25 pm
I have a rock that looks like there are little black spheres growing out of the surface in small colonies. Please help me I am so curious! I have a picture! The black bumps almost have a purple sheen to them.
@Honeybhunter,
send a picture but it sounds like Goethite or limonite. Those are the most common rocks with the Botroiydal or mamilary habit. They are usually iridescent blue purple black an are slightly magnetic (they are mostly complex iron multi-hydroxides. If you put em in an oven at 500F, all the color will evaporate with the intermolecular water
@Honeybhunter,
instructions for posting photos can be found
here ...
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