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Improving Mindat.orgCadmian Smithsonite

2nd Oct 2006 02:40 UTCJolyon Ralph Founder

Whilst going through a general cleanup and check of varieties, we realised there was a problem in general use with this name.

A lot of people are describing yellow smithsonites as "Cadmian Smithsonite".

This is wrong.

Cadmium Carbonate (Otavite) is white, so any true Cadmian Smithsonite would also be white. There is one photo, of a Tsumeb Cadmian Smithsonite, that looks genuine. Everything else is something different.

The something different was originally described as "Turkey Fat Ore". This described an appearance rather than a chemical composition, but the material, a yellow botryoidal smithsonite, does have traces of Cadmium, but as micro inclusions of Greenockite. So technically, those "Cadmian Smithsonites" that have been posted are actually a mixture of Smithsonite and Greenockite.

So if you have yellow smithsonites in your collection labelled "Cadmian Smithsonite", probably the best thing to do is cross out the word "Cadmian" and leave it as Smithsonite, you can add "with Greenockite inclusions" afterwards if you wish.

Thanks to Chet and Uwe for pointing this out to me, I assumed that we had it right before.

I've moved those photos from "Cadmian Smithsonite" that don't need to be there.

Jolyon

2nd Oct 2006 04:13 UTCJeremy Zolan

Cadmium has a full D shell and the transition metals that have full D shells or D shells with only 1 electron are transparent in coloration (usually)- the best examples of this property are the Zinc compounds, compounds of Cadmium (excluding non-oxygen species), and compounds of Scandium and Yttrium. Mercury occasionally fits this, but Hg compounds, although many clear (HgNO3, Hg-HgSO4, HgCl), some are brightly colored such as HgI and HgS so this is an exception to this rule. Cadmium only forms one compound that I know of that is colored- CdS. I'm assuming CdSe may be dark reddish-orange and metallic and CdTe would be quite shiny and metallic blue-grey but this is based on trends than on actual data. CdO (monteponite) is clear. Remember, Smithsonite may also be colored orange from limonite so if cadmium presence is doubtful in the specimen, do a test for cadmium (I don't know any, sorry).

2nd Oct 2006 09:57 UTCJolyon Ralph Founder

I thought about this afterwards - there is of course some chance that a smithsonite containing CdS inclusions may still also have additional Cd in the smithsonite structure, so it could still be Cadmian Smithsonite with Greenockite inclusions - but, this is important, it would probably be very difficult and expensive to prove this one way or the other - so my best advice remains to rename these as just "Smiithsonite"

Jolyon

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