[Rockhounds] safest wavellite cleaning method

[Clyde]

Hi Everyone,   My wife and I went to collect wavellite at Mt. Pleasant Mills quarry.  We found some pretty nice specimens and would like to get advice on cleaning them the safest and best way.  At minimum some have limonite coatings, others have a black coating that I don't know what it is.  I have Iron Out, Oxalic acid, and Muratic Acid available.  
Is there any tried and true method or formula?

Thanks in advance,

Clyde

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