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Jewelry, Gems, & Minerals/Stalagmite Curiosity


Hello.  About a month ago my friends son (9 years old) was asking about stalagmites/ctites.  We explained with a reasonable amount of confidence for a couple of Kansas farmers about water running though limestone and dissolving the minerals and then redepositing them on the ceiling and floor of the cave.  My research this past month has confirmed that I didn't lie to a child.  But he asked us a question that we just couldn't answer.  "Can you take some smashed up limestone and dissolve it in water.  Then strain out the big stuff and let it evaporate to make your own?"  I would think that it would be pretty crumbly but on the other hand the tips of stalagmites are quite hard and if the recently deposited portion was soft then wouldn't it break off or wear away before it could harden?  I guess what I'm asking is, what process sets the stalagmites?  Is there a process?  And is it possible to to make something akin to it at home?  I've found projects involving cloth and baking soda but I don't think this kid will be satisfied until he makes some from actual limestone.  

Thank you, John

An excellent and very inquisitive question :-)
Yes, it will work. It might even work better if you took a jar of water, got some straws and everyone is blowing bubbles into the water for 5 minutes. (Don't hyperventilate...) The carbon dioxide you exhale will dissolve in the water and will make natural carbonic acid, the same acid that occurs naturally in rainwater and is responsible for the dissolution of limestone.
So blow in the jar full of water for a few minutes, add limestone chunks and lets sit for a day or so. Filter out the big chunks, or pour just the liquid off into a shallow dish. Let sit and as the water evaporates you will see some chalky residue form. That is basically the beginning of a stalagmite / stalactite, alas not nearly as pretty.
The reason those beautiful limestone features form is the general sensitivity of the water with the dissolved limestone to minute chemical changes. As the water runs down slowly along a stalactite, minute quantities of water will evaporate. This in turn changes the chemistry of the water and the solid mineral calcite (calcium carbonate) precipitates in minute quantities out of the solution in layers onto the stalactite. As it drops to the ground, the same process is repeated on the floor forming stalagmites. Again, the precipitated quantities of calcite are rather small, this is why it takes so darn long for a nice big stalagmite / stalactite to form. By the way, if you cut a stalagmite / stalactite perpendicular to its length and polish the surface you may be able to see growth rings, not unlike those seen in a tree, depicting wetter and drier seasons of growth.
If the system is kept submersed in water and the evaporation / precipitation is very, very slow, you will get beautiful transparent to translucent sparkly calcite crystals. You may have seen those as ribbons in caves. However, for stalactites and stalagmites, if the material is not submersed but just moist and the evaporation is comparatively fast, the end product will have a much chalkier appearance, and will look more like the actually limestone.
Hope this helps. Good luck and have some fun with the experiment :-)

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Uwe Richard Kackstaetter, Ph.D. (Dr.K)


I can answer questions concerning minerals, mineralogy, gems, metals, and anything that has to do with geology. However, I am NOT a jeweler. Questions about values, settings, gem stone cuts and appraisals are best directed to other experts on this site. I can however aide in the identification of unknown mineral materials. As a public service and part as training for new geoscientists, our university department provides FREE mineral identification for individuals. Please contact me for details or go to for details..


I am a professor of applied geology and mineralogy with many hours of field experience. Furthermore, I enjoy recreational gold prospecting and mineral collecting. As a professor I am engaged in research concerning minerals and their occurrence.

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Ph.D. in Applied Geology and Mineralogy. I am actively teaching courses in mineralogy and a variety of field courses with mineral collecting opportunities. Background in precious metal exploration.

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