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Cleaning Dioptase

Cleaning Dioptase
June 28, 2011 06:36AM
Hello!

Report on cleaning Dioptase:

I tried to clean Dioptase crystal from a little matrix using a 30% HCl.

The Dioptase has melted and the solution is now full of a green gel...

-Kostas.
Re: Cleaning Dioptase
June 28, 2011 09:17AM
Never use HCl on any copper silicates. Dilute nitric acid is OK on dioptase, if you just want to remove calcite matrix.
avatar Re: Cleaning Dioptase
June 28, 2011 10:33AM
Always ask here before cleaning something in acid to avoid accidents like this. It's well known that dioptase decomposes in HCl



Edited 1 time(s). Last edit at 01/16/2014 08:23PM by Wayne Corwin.
Re: Cleaning Dioptase
June 28, 2011 02:11PM
Thank you all!

It was not an important piece,so Ihad no worries.

I just make sure I report,so that other members know that!


Thank you!~
avatar Re: Cleaning Dioptase
June 28, 2011 05:46PM
    
One of the old wet chemical tests was to put the unknown in HCl and see if a gel formed. It is fairly common for silicates to decompose.
Marc Maseman
Re: Cleaning Dioptase
June 30, 2011 08:59PM
When cleaning minerals, you should never use inorganic mineral acids (HCl, Sulfuric, Phosphoric, etc). Organic acids are typically much more user friendly. Based on what you are trying to remove, you can select the molecular size of the organic acid that will work on your particular mineral. Smaller molecules are more aggressive. Larger are less.

By organic and inorganic, I am not talking about organic in the sense of agriculture. In chemistry, we are are talking organic acids being ones that contain carbon. Inorganics contain no carbon.

Inorganics like HCL are one Hydrogen and one chloride. This is extremely volatile. An organic acid like citric acid is C6H8O7, which is obviously much, much larger and much less volatile.

From Wikipedia, some info on organic acids: Organic Acids on Wikipedia

Edit: No advertising please !



Edited 1 time(s). Last edit at 07/01/2011 09:12AM by Peter Haas.
avatar Re: Cleaning Dioptase
July 01, 2011 12:14AM
Unless you are using **gaseous** HCl, HCl isn't volatile. Aqueous HCl is H3O+ Cl-.

And there are plenty of inorganics with carbon. Calcite, for one.
avatar Re: Cleaning Dioptase
July 01, 2011 09:13AM
    
"Smaller molecules are more aggressive."

This is bare nonsense.
avatar Re: Cleaning Dioptase
July 01, 2011 11:03AM
If you try to remove calcite from dioptase using acetic acid, for instance, you will ruin the dioptase. There may be organic acids that will remove the calcite without harming the dioptase, but why experiment around when you know a cheap acid like nitric will work fine. Also, some organic acids are generally more expensive than inorganic ones (perhaps citric acid excepted). Some times however you may need to resort to them. Like when you are trying to dissolve calcite from around fossil spiders that have been replaced by Celestite.

Rock Currier
Crystals not pistols.
avatar Re: Cleaning Dioptase
July 01, 2011 02:09PM
Peter, I think the previous poster was confusing molecules with dogs.
Re: Cleaning Dioptase
July 05, 2011 11:37PM
Hi!

Any species (not to say any specimen) needs a specific acid.Some species can be cleaned by more than one acid.

If a compound is organic,then it contains Carbon.The opposite is not true.

To my knowledge,when an acid or a base is a solid salt,the aqueous solution vapors is water.So Citric acid cannot be less volatile at room temperature.

Steve,HCl solution isn't volatile?What the vapor consists of?
avatar Re: Cleaning Dioptase
July 06, 2011 03:08AM
    
Quote
Konstantinos Charalampidis
To my knowledge,when an acid or a base is a solid salt,the aqueous solution vapors is water

No. All components of the liquid phase are also contained in the gas phase (though at different concentrations). Even a ionogenic compound dissolved in water has a finite partial pressure in the gas phase above the solution, although this is exceedingly small. Anything else would be a violation of the second law.


Quote
Konstantinos Charalampidis
So Citric acid cannot be less volatile at room temperature.

Less volatile than what ?
avatar Re: Cleaning Dioptase
July 06, 2011 02:26PM
    
From the MRDS sheet for hydrogen chloride.:
Vapor pressure at 25C is 190 mmHg

You don't really want to breathe the fumes - very bad for the lungs. I have had metal corroded that was in proximity to closed bottles of muriatic acid (screw top plastic jugs).
Re: Cleaning Dioptase
July 06, 2011 03:56PM
    
Repost, sorry.
Re: Cleaning Dioptase
July 06, 2011 03:56PM
    
For quite a few purposes I think discussing HCl vs. H3O+Cl- is pretty academic. I'll second the dangers of corrosion of various times that someone (and/or me) has left HCl solution uncovered or with poor ventilation. The incident that comes to mind was the grad student who intensely disliked the smell of pyridine and so left an open container of dilute HCl in cabinet under fume hood to neutralise. Fast forward a week or two, there was incredible, cave-like corrosion (which got worse with time despite attempts to reneutralise and cover with protectant).
EMJ
avatar Re: Cleaning Dioptase
July 06, 2011 10:44PM
    
David Von Bargen Wrote:
-------------------------------------------------------
> From the MRDS sheet for hydrogen chloride.:
> Vapor pressure at 25C is 190 mmHg
>
> You don't really want to breathe the fumes - very
> bad for the lungs. I have had metal corroded that
> was in proximity to closed bottles of muriatic
> acid (screw top plastic jugs).

You should see my bathroom .. i once forgot a small open container with 10 % HCl and left for 2 weeks ... meanwhile the water evaporated and the concentration of HCl reached the "smoking" conc besides the "normal" HCl evaporation.. my metal fittings are a wreck now winking smiley and the atmosphere was at least hostile when i came back. Fortunately i had closed the bathroom door.
Re: Cleaning Dioptase
July 07, 2011 02:46AM
Hello!

Peter,thank you for correcting me.I've asked this question so many times and I always get a different answer.

Less went as an answer to the previous post claiming that Citric acid is less volatile than HCl and other acids.

Both solutions of Citric and HCl have odor (practically when I open the container,so I should have guessed that vapors are not just water (Citric).

Keep chemicals outside the house at a well protected places and the containers sealed as well.Animal and people can be harmed.

I've seen nervous system disorders due to working at chemical stores and all the bottles were closed.Keep all safety rules and ask here about them.

Everyone is asking about minerals and I only once saw a post about safety.

I remind everyone that NOT in all countries concentrated compounds are illegal and they are easy to buy.

I have a friend who had half his hand tissues necrotic after he tried to clean a specimen with Hydrofluoric and the glove was pierced.The doctors didn't know how to react and they didn't provide any Calcium medicament.I'm sure in the future he will face internal organ failure.Thankfully he's still alive.

I recommend that someone writes down an article about safety and it will be always visible for users of this forum.

-Kostas.
Molly Gove
Re: Cleaning Dioptase
January 16, 2014 05:49PM
I am not a chemist and am unfamiliar with acids. I have a piece that has dioptase crystals embedded in something else. There is some rust that is increasing and occluding the crystals.

What is a safe and accessible way to clean the rust off without hurting the crystals?

Thank you!
avatar Re: Cleaning Dioptase
January 17, 2014 12:59PM
Molly,
Could you give us a picture of the dioptase you hope to clean?

Rock Currier
Crystals not pistols.
Molly Gove
Re: Cleaning Dioptase
January 17, 2014 09:28PM
here is a photo... there is more rust now...

is there anything you know of to clean that will not hurt the dioptase crystals?

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