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Expert: C. Robert Reszka, Jr. - 11/4/2009


Question

I am looking to have this rock identified.  I was under the assumption it was a selenite.  Have my doubts now....  (smile).

Thank you for any help!

Answer
Hi Maureen,
This is an easy one.  Yes it is selenite.  It looks like a piece of a selenite rose, perhaps from Mexico.  That's a collection of selemite crystale.  Here's a pretty good picture of a selenite rose:

http://crystalseen.mybisi.com/product/0/LARGE-SELENITE-ROSE-FROM-MEXICO_80873.ht...


A Barite rose looks much like this, but usually it looks more uniform and more "flower" like. Here's a pretty good picture of a barite rose:

http://www.brightok.net/~rockman/Cleve/ClePhoto.htm

They may look alike but selenite is a calcium sulfate while barite is a barium sulfate.  Barite will feel heavier than it looks and selenite will be softer.  You should easily scratch the selenite, most likely with your fingenail.  A barite rose would not scratch as easily.

Hope this helps.
Bob
    Questioner's Rating
    Rating(1-10)Knowledgeability = 10Clarity of Response = 10Politeness = 10
    CommentThanks Bob! I am very happy it is a selenite! I know it is a very old sample... probably 50, 60 years old. This was a nice experience..... I am grateful.... :-) Maureen


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C. Robert Reszka, Jr.

Expertise

I can answer any general geology question (rocks, minerals, stratigraphy, geomorphology etc.). My expertise is in the geology of the Michigan Basin, PreCambrian, Paleozoic and Recent. I can answer questions concerning mining and petroleum exploration and production and the laws concerning those activities. I can also answer questions concerning stratigraphy of the Michigan Basin. I will also answer questions about mineral and rock collecting in the Basin. I won`t be able to answer many specific questions on hydrology, geophysics or geochemistry. I may be able to answer very general questions in those venues.

Experience

I have been working for the State of Michigan for 24 years as a Geologist and a Resource Analyst. I have experience with Subsurface Geology and Petroleum Geology, mining in Michigan, and Sand Dune Mining and Protection issues.

Organizations
Michigan Basin Geological Society

Publications
Decade of North American Geology.
Bedrock Geology of Michigan

Education/Credentials
BS Wayne State University

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