Unusual Rock - Knowledgebase Question

Quncy, Mi
Avatar for dmacklin
Question by dmacklin
June 3, 2008
I don't know if you guys would know this or not, but I was in West Terre Haute, IN this past weekend and while visiting family, I saw these unusual rocks in their yard. They were all the size of a soft ball (some a little bigger, some smaller) and they look like brains! They are yellow/brown in color and have brain-like crevices all over. Some are hollow inside and some have holes, but when broken open they have what looks like crystal inside. Any ideas? Any idea where I could go for information on them if you don't know? I'm putting them in my gardens because I think they are so unique. Thank you.

Answer from NGA
June 3, 2008
I think I know! What you describe is called Desert Rose Gypsum. They are clusters of gypsum crystals which have grown in sand and have inclusions of sand or earth in the crystals (hence the yellow/brown color). Gypsum is a hydrous calcium sulfate. It is translucent to opaque and is found in white or light tones of yellow, brown or red.

You can do a Google search or you can see photos of the different kinds at the following website:

Hope this information is helpful!

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