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daviddillman
Joined: 04 Dec 2010
Posts: 51
Location: Texas
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Posted: May 10, 2013 09:17 Post subject: Removing Iron Stains from Fluorite |
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I have some green fluorite I retrieved from an old tailings pile. The fluorite has been stained by what I think is iron in the soil. What are the best chemicals to remove iron stains from fluorite? _________________ DSD |
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Jordi Fabre
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Joined: 07 Aug 2006
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lluis
Joined: 17 Nov 2006
Posts: 711
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Posted: May 10, 2013 10:16 Post subject: Re: Removing Iron Stains from Fluorite |
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I agree with Jordi.
Just that I would add some sodium citrate as complexing agent.
With best wishes
Lluís |
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Peter Megaw
Site Admin
Joined: 13 Jan 2007
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Location: Tucson, Arizona
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Posted: May 10, 2013 10:18 Post subject: Re: Removing Iron Stains from Fluorite |
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Jordi is right...sold in US at most hardware stores as "Iron Out". It works best at elevated temperatures...crock pot is best. Put fluorite in water, heat it up, add IO let it run an hour or two, turn off and let it cool slowly. _________________ Siempre Adelante! |
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chris
Site Admin
Joined: 12 Jul 2007
Posts: 538
Location: Grenoble
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Posted: May 10, 2013 11:58 Post subject: Re: Removing Iron Stains from Fluorite |
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Quote: | turn off and let it cool slowly. |
I would say VERY slowly because a heated mineral doesn't like heat shock at all.
Chris |
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lluis
Joined: 17 Nov 2006
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Posted: May 10, 2013 12:16 Post subject: Re: Removing Iron Stains from Fluorite |
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Hi, Peter
Just as chemist, sodium dithionite oxidizes very quick with oxygen of air, so, a long time does not help too much.
Also, it decomposes very quick in acidic solutions. Done that when oxidizing creates sulphuric acid, decomposition rate increases exponentially (another help with sodium citrate is that acts as a buffer, maintaining a decent pH).
Heating, it decomposes also very quick.
And as last remark: sodium dithionite, if gets wet, can (and many times do...) burnt....
With best wishes
Lluís |
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trtlman
Joined: 28 Jun 2011
Posts: 172
Location: Washington
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Posted: May 10, 2013 13:43 Post subject: Re: Removing Iron Stains from Fluorite |
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I don't know about fluorite but Iheard products such as lime away and CLR can be used on quartz and other crystals. I do not know the chemical makeup of these cleaners so before trying perhaps someone on here could give a little more info on whether or not these products are sutible for fluorite. _________________ Daniel |
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Jesse Fisher
Joined: 18 Mar 2009
Posts: 629
Location: San Francisco
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Posted: May 12, 2013 12:32 Post subject: Re: Removing Iron Stains from Fluorite |
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Sodium dithionite works well at room temperature. A soak of no more than 8 hours usually will do the trick. I only add citric acid if the stain is particularly heavy. If the solution becomes saturated with iron, it can redeposit back into the fluorite and acidifying the solution will help prevent that from happening.
What ever you do, do not put fluorite in anything that contains oxalic acid. It will remove the iron stain but can also etch the fluorite. |
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daviddillman
Joined: 04 Dec 2010
Posts: 51
Location: Texas
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Posted: May 12, 2013 13:20 Post subject: Re: Removing Iron Stains from Fluorite |
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Everyone,
Thanks for the advice and the warning about not using oxalic acid.
David. _________________ DSD |
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bob kerr
Joined: 13 Nov 2011
Posts: 537
Location: Monroeville PA
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Posted: May 12, 2013 19:16 Post subject: Re: Removing Iron Stains from Fluorite |
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"What ever you do, do not put fluorite in anything that contains oxalic acid. It will remove the iron stain but can also etch the fluorite."
Huh? oxalic etches fluorite? no way will oxalic etch fluorite. where did you get or observe this happening? could you possibly have observed oxalic removing something from the surface of fluorite such that it LOOKED like it etched it??
bob |
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Jesse Fisher
Joined: 18 Mar 2009
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Posted: May 12, 2013 20:29 Post subject: Re: Removing Iron Stains from Fluorite |
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Oxalic acid will, indeed, etch fluorite. This occurs by the removal of calcium from the surface of the fluorite to form calcium oxalate. If you don't believe me, try it yourself. Just put a lustrous fluorite crystal in warm oxalic for a few hours and observe the result. |
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bob kerr
Joined: 13 Nov 2011
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Location: Monroeville PA
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Posted: May 12, 2013 21:41 Post subject: Re: Removing Iron Stains from Fluorite |
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I think there's a terminology issue here. IF the fluorite has calcium on the surface oxalic (and many other) acids will remove it and possibly leave behind a surface that appears to be "etched" - but I don't think this is the definition of etching. etching actually removes the base material (CaF) and oxalic just can't do that.
bob |
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Jesse Fisher
Joined: 18 Mar 2009
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Posted: May 12, 2013 23:42 Post subject: Re: Removing Iron Stains from Fluorite |
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Call it what you will, but oxalic acid has a strong affinity for calcium. I have ruined some good fluorites trying to remove iron stain with oxalic acid and will not do it again. Should you care to try, however, be my guest. |
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Pierre Joubert
Joined: 09 Mar 2012
Posts: 1605
Location: Western Cape
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Posted: May 13, 2013 02:45 Post subject: Re: Removing Iron Stains from Fluorite |
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Jesse Fisher wrote: | Call it what you will, but oxalic acid has a strong affinity for calcium. I have ruined some good fluorites trying to remove iron stain with oxalic acid and will not do it again. Should you care to try, however, be my guest. |
Hi Jesse. I have used Hydrochloric acid, with some success, to clean Fluorite crystals.
a Quick dip of calcite crystals (that have been dulled by Oxalic acid) in Hydrochloric acid, re moves the 'dull layer'. _________________ Pierre Joubert
'The tree of silence bears the fruit of peace. ' |
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Pierre Joubert
Joined: 09 Mar 2012
Posts: 1605
Location: Western Cape
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Posted: May 13, 2013 02:48 Post subject: Re: Removing Iron Stains from Fluorite |
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Pierre Joubert wrote: | Jesse Fisher wrote: | Call it what you will, but oxalic acid has a strong affinity for calcium. I have ruined some good fluorites trying to remove iron stain with oxalic acid and will not do it again. Should you care to try, however, be my guest. |
Hi Jesse. I have used Hydrochloric acid, with some success, to clean Fluorite crystals.
a Quick dip of calcite crystals (that have been dulled by Oxalic acid) in Hydrochloric acid, re moves the 'dull layer'. |
Sorry, I have to ad: I have not noticed any effect from Oxalic acid on Fluorite. _________________ Pierre Joubert
'The tree of silence bears the fruit of peace. ' |
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GneissWare
Joined: 07 Mar 2008
Posts: 1287
Location: California
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Posted: May 13, 2013 08:09 Post subject: Re: Removing Iron Stains from Fluorite |
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I am not an expert on cleaning Fluorite, but am certain Jesse has cleaned more Fluorite than most people on the planet. Although some Fluorite may be safe to clean in oxalic, the lessen is that not all Fluorite is safe in oxalic. This is true for many minerals. They are not lab-grown, perfectly pure products of uniform composition. Thus, a Mineral X from one locality may be cleaned perfectly with Product Y, but Mineral X from a different locality may be damaged by Product Y.
You should always test a sample from the locality you are cleaning before cleaning the entire batch, unless you already know how to clean from that locality. Jesse _knows_ that Fluorite, presumably from the Rogerely Mine, and likely many others, should not be cleaned in oxalic acid, hence the warning. |
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Pierre Joubert
Joined: 09 Mar 2012
Posts: 1605
Location: Western Cape
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Posted: May 13, 2013 08:39 Post subject: Re: Removing Iron Stains from Fluorite |
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GneissWare wrote: | I am not an expert on cleaning Fluorite, but am certain Jesse has cleaned more Fluorite than most people on the planet. Although some Fluorite may be safe to clean in oxalic, the lessen is that not all Fluorite is safe in oxalic. This is true for many minerals. They are not lab-grown, perfectly pure products of uniform composition. Thus, a Mineral X from one locality may be cleaned perfectly with Product Y, but Mineral X from a different locality may be damaged by Product Y.
You should always test a sample from the locality you are cleaning before cleaning the entire batch, unless you already know how to clean from that locality. Jesse _knows_ that Fluorite, presumably from the Rogerely Mine, and likely many others, should not be cleaned in oxalic acid, hence the warning. |
Wise words Bob! Thank you! _________________ Pierre Joubert
'The tree of silence bears the fruit of peace. ' |
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