FMF - Friends of Minerals Forum, discussion and message board

[h.abbasi]

Hi All,
How I can remove dusty ( not Calcite and not solve in Chloridric acid) from surface of this fluorite specimen, Please?
Thanks a lot,

[kushmeja]

I've seen and have similar fluorite specimens with a coating like that, and I don't believe there's a way to remove it without damaging the fluorite crystals. The coating on the ones I've seen appears to be inter grown with the topmost layers of the fluorite crystals as well, so at least on those, I don't believe you could ever remove it without causing significant damage to the underlying crystals' surface.

[GneissWare]

Its probably a silica coating, which can be removed with some dangerous chemistry.

[Bob Harman]

I think what both GneissWare and Kushmeja say may be true. The coating on your fluorite might.....and I emphasize might.....be removed with some harsh chemicals such as hydrofluoric acid if it is silica, but it might not leave the crystal surfaces of the fluorites smooth and glassy. They might.....and I again emphasize might..... look dull and pitted. Bottom line for me is if you wish to try, do a low end specimen or small corner of this specimen first. Hope this helps. Cheers.....bOB

[h.abbasi]

I was able to move them with a needle. But this is time consuming and may also cause damage to the crystals

[kushmeja]

If you're able to scrape the coating off that easily, it's not what I thought it was. Using a high pressure water gun or air gun with the plastic pellets will probably work.

[h.abbasi]

I have more same specimens to clean ...!

[h.abbasi]

[lluis]

Hi, Abbasi

Was said that fluorhidric acid (very dangerous! a drop in flesh and the burning is very hard to cure and the scar could be more than big. It also eats any silicate. So, only plastic...or inert materials to it to be used.... Not a good idea, anyway) could clean the crust, if it is a silicate.
If any calcium is there, you will change the crust by a dusting of second generation fluorite, man made, that would not be easy to take out.

I tried one time to clean a Dalnegorsk fluorite of some quartz, and I get that...
But cleaned piece lacked aesthetics it had before cleaning.....
So, in case you decide to play risky, take all precautions and do it first with a small piece that you do not mind to damage...
Cleaning after acid bath should be done with distilled water.....if you do not wish to have a dusting of secondary fluorite man made.

Again, fluorhidric acid is very (VERY!!!!) dangerous, and better not touch it....

With best wishes

Lluís

[h.abbasi]