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Round Rock, makes a rattling noise when shook


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I have a round rock that I found out in the desert in Lancaster, California. When I shake it, it soundS like there’s water inside with something else rattling inside. If you could please assist me with finding out what’s making the noise before I break it open, I would really appreciate it.




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It may be a geode. Geodes are rocks that are hollow, and can have some sort of crystal formation inside them. If something has broken off inside, that could be the rattle you hear.


"Geodes can form in any cavity, but the term is usually reserved for more or less rounded formations in igneous and sedimentary rocks. They can form in gas bubbles in igneous rocks, such as vesicles in basaltic lava; or, as in the American Midwest, in rounded cavities in sedimentary formations. After rock around the cavity hardens, dissolved silicates and/or carbonates are deposited on the inside surface. Over time, this slow feed of mineral constituents from groundwater or hydrothermal solutions allows crystals to form inside the hollow chamber. Bedrock containing geodes eventually weathers and decomposes, leaving them present at the surface if they are composed of resistant material such as quartz.[1]

When cut in half, visible bands corresponding to varied stages of precipitation may at times show patterns that reveal points of fluid entry into the cavity and/or varied colors corresponding to changes in chemistry."


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  • 2 weeks later...

I hope you will find someone with a rock saw to open it up for you. I've seen a few hammer and chisel attempts that were regrettable with what would have been a display of spectacular crystals being smashed to bits. I've also used my wet tile saw on some smaller examples with acceptable results. 

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They call them 'Thundereggs' where I come from and there is even a nearby tourist park that allows fossicking in an open air mine.

As long as you have a go and dig deep, you will find your treasures! Thundereggs make up 97% of the mine. It is a very rich and dense Thunderegg Deposit and has only had roughly 10% removed since being opened to the public in 1967. According to specialists, the Thunderegg Deposit is 400m deep which will allow for around 800 -1000 years of fossicking, so there are plenty thundereggs still to find!



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