FMF - Friends of Minerals Forum, discussion and message board

[AleaBankston]

Hello! I purchased this citrine geode sphere a couple weeks ago, and it came with a white coating on the druzy. I'm not sure if its calcite or something else. I'd like to remove it to expose the citrine druzy, but I'm not sure how to go about doing that. I tried soaking it in white vinegar for a week, and I tried scraping at it with a steel brush. I've only been successful in knocking off a few little chips of it so far. Is there a solution I could use that would dissolve the white stuff without dissolving the cement on the back side of the sphere?

[James Catmur]

It is hard to know what the coating is.

Assume it started life as Quartz/amethyst and was heat-treated to get this color. Not calcite, as you have found out so I am not sure what it is or how to remove it

[vic rzonca]

Most of the Brazilian "citrine" starts out as inferior amethyst that is heated to bring out the orange color. The coating is another generation of quartz. Short of advanced acid etching techniques, using very nasty reagents, you may have to learn to love it. I've had your problem on an interesting amethyst I acquired. I lived with it.

[AleaBankston]

Aww bummer, was really hoping it was something I'd be able to get rid of. Guess I'll still be on the hunt for a citrine geode sphere because I really wanted to be able to see the citrine clearly. Ahh well! Anyway, thank you to both of you guys for responding. 😊

[SteveB]

An aside question, coatings on crystals similar to this can sometimes be surface staining that can be removed with a household Calcium, Lime, Rust remover solution. For crystals that have something more persistant I was wondering if more harsh removal options, if they worked, would leave the crystal surfaces pitted and ugly not smooth and shiny?

[lluis]

Hi, AleaBankston (any name? I always heard that to sign a message in Internet is considered polite... And I feel dumb addressing to a nick.... :-( )

As James said, it is probably (likely sure...) a former amethyst heated to look like citrine.
As Vic said, I think also it is a second generation of quartz or maybe a second generation of another silicate...

To clean quartz over quartz, as he says also, it is quite difficult...

Maybe, if you are extremely careful and wear gloves and protective lenses, you could try the method reported many years ago in Lapis for cleaning some dirtiness...

Prepare a solution of 10% sodium hydroxide, Let it cool at room temperature. Place the sphere inside, and heat the solution slowly until a temp of around 80ºC is reached. Leave the sphere in this bath for 5-6 hours, checking several times to see how the item looks...
When time passes, let if cool slowly, discard the solution (be cautious! Sodium hydroxide is very caustic and has the disagreeable property/behaviour to get inside skin, so it continues burning tissues even if cleaned with running water,,,,!!!!!), rinse with running water and place in water with some vinegar. After several hours, discard, and place again in another solution of vinegar in water. Do this several times. Then brush the rest of adherence, in case it still exists....

As a caution, try first on a piece of similar material that you do not care if it gets damaged...
The slow heating and slow cooling is designed to avoid breaking the piece, but the crystals, well, could consider that they are abused and break apart... So, better be sure before doing anything...

Other, generally safer, is do as Vic did: live with the crust....

Sorry, but as said, it is hard to clean quartz over quartz, and also to clean a silicate over quartz (unless silicate is a zeolite, which I doubt is the case....)

With best wishes

Lluís

[AleaBankston]

Lluis, hello! My name is Alea (last name Bankston). 😊

[lluis]

Hi, Alea

My pleasure!

I was thinking if Alea was your name, but I was thinking also that alea in latin is chance ...and I begin to think that maybe not a name...
My fault

Enjoy the group!

With best wishes

Lluís

P.D.: by the way, I was thinking that the crusts maybe are kaolinite just burnt when making the "citrine". Maybe it would go with the solution (I think so...), but still is the question of how sensitive to temperature the sphere is.