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Author: Subject: Formation of limestone stalactites
Admagistr
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[*] posted on 24-1-2022 at 15:49
Formation of limestone stalactites


I'm doing an experiment to study karst phenomena. I dissolved finely ground limestone from the local quarry Vitosov near Zábřeh in Moravia in water and CO2 introduced from a pressure bottle called "Sodastream" intended for food purposes in a washer via a frit. The food grade CO2 is very pure. I first tried to soak a cotton wick as thick as my thumb with the solution obtained by it, but the wick did not absorb the solution. Then I found some cave sinter from the Vitosov quarry at home and had natural Ca(HCO3)2 drip onto it via a frit filter cup, but unfortunately I have had no success so far. As a by-product of dissolving the limestone I was left with an ugly grey clay... There are small stalactite caves in the quarry, but only a select few mine and collect stalactites there. I don't have any friends there, so I decided to go this route for the Vitošov stalactites... Do you have any idea what to do to make the experiment a successfull? It takes a long time to form stalactites in caves, but the humidity is much lower at home and using a concentrated Ca(HCO3)2 solution I thought it wouldn't be a big problem and would go well, but so far I haven't had any success...
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[*] posted on 24-1-2022 at 17:31


Very very slowly drip your solution onto the stone.
Time your drops so the first will dry before the next falls.


The idea is to use solubility to change the shape of the rock. To much liquid too fast will result in removing material. If you can get the water to form a drip without dropping. Thats the perfect rate.

If you suspended the limestone with a string. Then drip your solvent down the string. The rock will absorb the string. Its quite cool but will take days before a result can been seen.




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[*] posted on 25-1-2022 at 18:25


Quote: Originally posted by Rainwater  
Very very slowly drip your solution onto the stone.
Time your drops so the first will dry before the next falls.


The idea is to use solubility to change the shape of the rock. To much liquid too fast will result in removing material. If you can get the water to form a drip without dropping. Thats the perfect rate.

If you suspended the limestone with a string. Then drip your solvent down the string. The rock will absorb the string. Its quite cool but will take days before a result can been seen.



Yes, that's probably the problem, I let the solution drip too fast... Thanks for the valuable advice, I'll do it that way, when I have some result, I'll send photos.
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[*] posted on 25-1-2022 at 22:47


you could grow your stalactite on something like an electric heater
for a much higher evaporation rate hence rock growth rate.
use a power/pwm/dimmer/pid/temperature controller.

usual electricity + water safety precautions




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[*] posted on 26-1-2022 at 01:46


Bear in mind that they are incredibly sensitive to contamination. For example if you get any oil from you skin on them they will like stop growing.
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[*] posted on 26-1-2022 at 13:42


Quarries, bunkers, mines and all kind of underground man made constructions have been my main hobby for the past 30 years.
Unfortunately I dont know most of the english names for all the different stalagtites, stalagmites, draperies and other formations.

But just have a look at soda straw stalagtites up close. Those are usually found in places where rain pours from the ceiling (not just one source) and with a lot of minerals. They are way more abundant if the ceiling is concrete and not rock or stone masonry.
They have water running inside and out (most of the time, or at least while they develop).

It's not the water that needs to evaporate but the CO2 dissolved in the water that needs to go for the calcite to drop out.
By evaporating water you just create a mess of dry salts not a formation of any sorts.

Another example: petrifying barrels.
These are man made by local farmers, explorers etc. Basically take a 55gal drum, a barrel or a bucket, made of steel or wood it seems to make no difference and place it somewhere to collect water dripping from the ceiling in your nearby quarry. You need a steady flow but not as much as it will disturb the water once the barrel is full.
Come back 10 years later and you will find yourself staring at the inside of the barrel full of cristals growing as a mineral romanesco cabbage. These things are amazingly beautiful and I always spend a long time looking at these fractals growing on the inside.

I've also seen people use big PVC agricultural tubing to bring water from a place where there are already formations to somewhere else a bit further. Just for the kick of making new formations for the next generation !
That's at least a 10 or 20 years project if you're just helping nature a little bit.

In my opinion, there are two crucial things that will be missing from a hobby setting.
- Absolute stillness otherwise you'll get a fine mess as if you were stirring while cooling a salt solution.
- No air movement or constant air movement in one direction only. I guess that could still be mitigated though.

That last one became particularly clear to me in a KCl mine with 2 entrances which made the wind flow alternate between seasons. KCl grows very fast so stalatites where "z" shaped and you could litterally "read time" on them.




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[*] posted on 26-1-2022 at 17:48


Inside of old water heaters is another good place to find these formations. Mostly, when the unit is supplied from a well. I was taught that the primary mechanism of formation was the least soluble material being forced out of solution either by decreased volume, temperature change, or the addition on a more soluble compound. When i visited the caves in West Virginia. There was the strong smell of sulfer and amonia. Maybe the liquid reaches the atmosphere inside the area, absorbs some of these gasses. Then forcing minerals out of solution.



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[*] posted on 26-1-2022 at 19:32


Thank you all for the important advices, I was especially interested in the idea of regulated heating...Stalactites in caves are formed from acidic solutions and those formed by corrosion of concrete have exactly the same chemical composition - almost pure CaCO3, but a different internal structure. Also, these stalactites do not arise from acidic solutions as in nature, but instead arise from opposite, alkaline solutions! Natural calcite/aragonite stalactites release CO2 during their formation and the anthropogenic ones, formed from concrete, receive CO2!
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[*] posted on 4-4-2022 at 00:17


Hello, if you have issues knowing the English names, you can learn them quickly https://ksa.mytutorsource.com/blog/how-to-learn-english-fast...
Anyway, I read this thread and was very interested in what exactly karst is. For newbies like me here is an intro.
The dissolving of soluble rocks such as limestone, dolomite, and gypsum creates karst terrain. It's known for its sinkholes and caverns, as well as subsurface drainage networks. Given the correct conditions, it has even been observed for more weathering-resistant rocks like quartzite. With few or no rivers or lakes, subterranean drainage may reduce surface water. However, in areas where the dissolved bedrock is covered (perhaps by debris) or constrained by one or more non-soluble rock layers, unique karst characteristics may only be visible at subterranean levels and may be completely absent above ground.
Calcium carbonate-containing rocks (limestone, marl, and dolomite) are likewise dissolved, but this time with the addition of carbon dioxide. The phenomenon of water dissolving rocks is known as the karst phenomenon. Ice is an excellent illustration of karst phenomena (glacial karst, cryokarst). Although the methods of disintegration of various types of rocks and ice differ, the common feature of all karst events is the formation of forms both on the surface and underneath.
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