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My aunt gave me this rock. She has had for years. She was given it by a relative who passed many years ago. She said it was called a Tuffy (not sure which way it should be spelled) and that it came from Neveda. I couldn't find any info on it. Could you help. Thank you.

enter image description here

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  • $\begingroup$ You need at least one more photo from a different angle with coin or ruler to show scale. Also some idea of weight and hardness. Ideally some info on the site, but that seems impossible in this case. It didn't come from an old nuclear test site by any chance? $\endgroup$ – Michael Walsby Sep 26 '19 at 16:48
  • $\begingroup$ From what I understand, no it didn't come from a nuclear test site. I will get more pictures posted later today. It is very heavy. I can lift up to 50 lbs., and I can't even start to lift this one. Thank you for comments. $\endgroup$ – GarD-ner8 Sep 26 '19 at 16:57
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Typically we are not answering Rock Id questions, though this is a somewhat unique question because the rock is unique. Your rock is likely a tufa (never heard it called tuffy). It is a rock that is formed when water with high carbonate content is released to the surface. Depending on the conditions at the surface the dissolved carbonate comes out of solution, this can be through cooling, depressurization and reduction of the partial pressure of CO2, or through biological precipitation by organisms such as blue-green algae. There may also be other means that the deposition occurs but overall the water solution is initially oversaturated with the carbonate minerals. These deposit out in the patterns shown on your sample. If you were to perform an acid test your rock should show a strong reaction. The area around the California Nevada boundary has a large number of locations with this type of deposit both active, Mono Lake, and inactive like the Trona Pinnacles. Nevada itself has some of these deposits in the Black Rock Desert, Pyramid Lake and Fly Ranch areas. Deposits are likely found world wide but these are the ones I am familiar with. The pattern of deposition on your rock suggests to me an association with algae when it was deposited. See the following sites:

https://en.wikipedia.org/wiki/Tufa

https://www.blackrockdesert.org/wiki/index.php?title=Geology

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