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I have this piece of tumbled smoky quartz (Silicium oxide with entrapped materials giving it its black color). I accidentally left it in my clothes and it ended up in our washing machine. The detergent left a dull residue on the stone, taking the shine away.

I tried to clean it with water and afterwards with a dry cloth to rub the residue off, but both to no avail. Could anyone advise me how to clean my quartz without damaging it further?

Alternatively, the washing process may have chemically affected my specimen? The washing detergent is probably basic and silica can react with hydroxide. The temperature was cold to warm (forgot the exact program that was used).

smoking quartz
Two specimens of smoky quartz. The left one is affected by the washing process.

Catija
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AliceD
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    I'm not actually certain that it's a residue. It may have actually removed the tumbled polish from the stone... It may be necessary to re-tumble it. – Catija Jun 08 '17 at 15:51

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If it is residue white vinegar should remove it. Gentle rubbing with wet Bon Ami powder also takes off combination gunk from things like fabric softener. Laundry detergent isn't usually strongly alkaline enough to etch silicates.

kamala
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  • Thank you! I very carefully tried cleaning-vinegar (somewhat stronger than kitchen vinegar) and it seemed to work, but I was kind of afraid to do it rigorously. Now I'm reading your post I'll try a somewhat more thorough vinegar-rinse and I'll keep you posted on the progress! Are you sure acids are safe on silica minerals such as smoky quartz? – AliceD Jun 13 '17 at 20:25
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    I haven't tested smokey quartz myself, but silicates generally react with bases, not acids. Soap and detergent are weakly alkaline, not acidic. That's why you can see 'etching' from dishwasher detergent on some glass after multiple washings. The aluminum that makes smoky quartz 'smoky' could be mildlyreactive but I don't think there's enough in there to cause surface pitting. BTW, thanks. Thinking about this has suggested a possible fix for polished slilica based stones that are too shiny. – kamala Jun 15 '17 at 01:23