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  Author   Comment  
Bill K.

Took my kids to explore the caves in Mammoth Cave area in Kentucky. Had a blast and even went Geode hunting. Could not find any so we bought some unopened ones at a local roadside shop. I would like to know what they are exactly and where do you think they came from. We really love them. Not sure if they are smoky quartz or something else. I'm sure they are not worth anything but we love them just the same. Would love some info just for the sake of knowing what we do have.

Thank you,

Bill K.

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Bob Harman
BILL K,    From your photos, it looks to me like all your examples are "coconuts".   This is the common term used for a type of igneous geode from a locality in Chihuahua State, Mexico. They are called "coconuts" as they are quite round and  their outer surface vaguely looks like a coconut.   The inside shows quartz. A couple may have light smoky quartz while a couple of others might have very pale amethyst quartz.  I don't see any calcites or other secondary minerals.
 They are nice, but rather ordinary; your examples, opened, might sell for $25 at dealers or touristy gift shops. Enjoy them as they just might spur your interest in finding more examples.     Happy New Year,   BOB
Bill K.
I just had someone tell me that they might be celestite. That would make sense if they were from a local Kentucky roadside shop. What do you think?
Bob Harman
No No No !    They are Mexican "coconut'" geodes. Quartz on the inside and not celestite and not from Kentucky. Just google "Mexican coconut geodes" and you will find many many pictured examples, some of which are virtually identical to your examples.  Mexican geodes are very commonly found in roadside rock shops.   BOB
Bill K.
Inside some of them they have VERY white crystals. The white does not wipe off. Are they a different mineral? When I first opened them, I thought they were dirty. Some even had clay/mud inside them. I soaked a couple of them in Iron Out for a few days and nothing changed about them. Color stayed the same, even the white crystals.

Bill K.
Bob Harman
And, for those interested in celestite (celestine) geodes, I should add that this mineral is found as much different crystals in Indiana geodes from 2 locations; the Hoosier Stone Quarry in Salem, Washington County (now closed and flooded) and Lehigh Portland Cement Quarry in Mitchell Indiana, Lawrence County. Also nice examples are from Wymore Nebraska, Gage County in the  extreme SE part of that state.  
I don't think celestite is found, looking anything like your examples, anywhere in Kentucky geodes; if it is found in Kentucky geodes at all. To see Midwest geode examples go to the websites "Fabremineral forum".com and go to "a mineralogical trip thru the states of the USA". Then on to Indiana. Or you can go to "" and look up "celestine in Midwest geodes"     Hope this helps.   BOB.
Bob Harman
The white coating might either be aragonite, a carbonate crystal polymorph similar to calcite or one of several clay minerals including kaolinite that are commonly found as coatings on quartz in geodes. Try some household vinegar to remove the coating; it might work.     BOB
Bill K.
This is one with the white crystals.

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Bill K.
The person who mentioned Celestine said possible Put in Bay area of Ohio. I'm looking at Mexican Coconut Geodes right now. Thank you very much for the research info.

Bill K.
Bob Harman
Bill K     I hate to rain on your friend, not only is his identification wrong, but his locality of Put-In-Bay, Ohio is incorrect as the geology is wrong for geodes. Celestite is common in Ohio quarries, but geodes are just not found in nearly all of Ohio.    For a USA map showing most geode sites go to the "Midwest USA Sedimentary Geode" thread on the website There is a map from March 13, 2013 showing the sites. My computer shows the map at the bottom of page 2 of that thread.    BOB
Bill K.
Thank you so very much. I love the info you gave me. Now I just have to plan a successful geode hunting trip [wink]
bill K.
I contacted the shop where I bought them and they answered. This is what they said: "Bill, wow, those look pretty awesome. Thank you for sharing the pictures with us. Most of our bigger geodes come from Northern Mexico, and your pictures look like what I would expect of those. We have smaller, very light weight ones that are from Morocco. These are very thin and very snow white crystals. Glad you enjoyed these geodes. Happy New Years Bill." You were right, they are Mexican.

Bill K.
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