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GeneralGeneral observations on smithsonites

25th Nov 2016 13:30 UTCPaul De Bondt Manager

Hi,

I noticed that quite a lot of smithsonites are put in the general smithsonite gallery.

I see a lot of pink, green, blue and other colors in there, like de Choix specimens, but the page only list " smithsonite ".

Does anyone knows what impureties gives this colors in these specific smithies ?

Should the Choix page been updated ?

All information is greatly appreciated.

Paul.

25th Nov 2016 13:44 UTCDavid Von Bargen Manager

For Larium see: https://www.researchgate.net/profile/P_Voudouris/publication/260159399_Lavrion_smithsonites_A_mineralogical_and_mineral_chemical_study_of_their_coloration/links/0a85e52fcf46677a50000000.pdf

http://periodicodimineralogia.it/doi/2015_84_2/2015PM0019.pdf

25th Nov 2016 14:26 UTCJamison K. Brizendine 🌟 Expert

I made a comment a few years ago about smithsonites labeled from the Santa Anita Mine (http://www.mindat.org/loc-13532.html). This was my original statement:

In the article, Wilson (2011, 455-456) points out (through his personal communication with Mario Ayub Touché) that the Santa Anita Mine never produced any smithsonite and in fact any smithsonite that was labeled from coming from that mine actually came from the nearby El Refugio Mine (http://www.mindat.org/loc-158664.html).

I seem to be a bit confused because there are several specimens of colorful smithsonite on mindat’s photo database assigned to this locality and several of them were stated to be “found” in 2005. Mexican minerals are not my specialty and I just wanted to confirm whether or not any other literature either refutes or agrees with Wilson’s (2011) comment that smithsonite was found at the Santa Anita Mine.

Sources:

Wilson, W., 2011, The Refugio Mine: Municipio de Choix, Sinaloa, Mexico: The Mineralogical Record, v. 42 (5), p. 453-461.

This was Rock Currier's comment:

I am pretty sure that Wendell Wilson is correct and I would change your labels accordingly and upload them to the correct mine. The others in our data base need to be changes also. I wish all of the people adding data and images to our site were as careful as you are.

I think Rock was planning on transferring the photographs from the Santa Anita Mine page to the El Refugio Mine page, but it never happened as he was working on other (and frankly more important) things than this. I thought since Paul introduced this topic on Mexican smithsonites, I felt it was pertinent to bring this back up.

27th Nov 2016 00:18 UTCJim Robison

David I found your comments above after I responded to Paul's other thread on smithsonite color. Thanks for including the two references. I wonder if you have found any for Tsumeb. I've never seen any from there. What is needed here, as in many other instances, is somebody willing to take on a research study. I owe Virgil Lueth some small samples of Tsumeb smithsonite so he can try a study similar to the ones you found. Too many health distractions this past year.

28th Nov 2016 03:36 UTCJim Robison

Further to the smithsonite color discussion, Paul De Bondt had about the same time started this thread. David Von Bargen gave a couple of useful links, which I downloaded and read through last night. One is highly technical and was well above my head, but in this paper (Samouhos et al) from Periodica de Mineralogia, included some possibly helpful comments about some studies on 'Namibian' smithsonite by several authors. I am hoping somebody can get me a link to the papers, listed in the bibliography, as described below.

Frost R., Hales M. and Wain D. (2007) - Raman spectroscopy of Smithsonite. Journal of Raman Spectroscopy, 39, 108-114.

Frost, R., Reddy B., Wain D., and Hales M. (2006) - An application of near infrared spectroscopy to the study of carbonate minerals - smithsonite, rhodochrosites, spaerocobaltite and cadmium smithsonite. Journal of Near Infrared Spectroscopy, 14, 317-324

Frost R., Reddy B., Hales M. and Wain D. (2008) - Near infrared spectroscopy of the smithsonite Minerals, Journal of Near Infrared Spectroscopy, 16. 75-82.

I hasten to add that when it comes to the subject of spectroscopy in general and the above in particular, I have absolutely no clue what the technical data is about. What I am looking for is references to color study in smithsonite, and specifically where in Namibia the specimens studied came from.

As a long time student of the carbonate minerals, whenever I can add to my knowledge data base I like to do so. What seems abundantly clear in the references read so far is that the studies of color are complex, and specific to the sample studied. I get the distinct impression that another similar appearing specimen would require detailed study as well, and that even for the same mine, the conclusions reached might be different.

Both of David's documents were helpful to me in gaining a little more understanding of the subject. I hope the above papers may be useful as well.

Incidentally the Virgil Lueth study I mentioned in the other thread was also in the bibliography,

Frish P., Lueth V. and Hlava P. (2002) - The colors of smithsonite" A microchemical investigation. New Mexico Geology, 24, 132-133

29th Nov 2016 11:25 UTCKeith Compton 🌟 Manager

Hi

There is a brief article on the colour and causes of colour of Smithsonite in Lithographie's Issue 13: Smithsonite - Think Zinc!

The article is by Virgil Lueth and Patrica Frisch.

Cheers

Keith

29th Nov 2016 13:34 UTCRalph S Bottrill 🌟 Manager

For the majority of us without acess to these often obscure journals, is it possibly to get pdfs, or at least a quick summary of each article? Maybe a tabulation of colours vs chemistry would be very elucidating?

30th Nov 2016 02:55 UTCJim Robison

Ralph, access to obscure journals is exactly my problem. What I know and understand about Raman spectroscopy and all the other techniques that fall under the journals I mention would fit under the head of a very tiny pin. However, the papers in David's original post above, and I am hoping in the ones I am looking for, likely contain a paragraph or two under conclusions that says what I am searching for, which is a description of what causes the color in the specimen studied. I've looked at enough of these short descriptions to know that the causes of color are complex. A tabulation would have to include a picture of the specimen described, its exact location, etc. I'm content at this point to see what some of the conclusions are. Virgil Lueth's article, including the Lithographie example described above, were layman oriented, and reasonably straight forward, though based on some very competent science.

The exhibits at the Tucson show with a "blue' theme in some instances discussed the causes of the colors. My recollection is that most often the cause was some molecular property of a mineral, and may be fairly constant from location to location. In the case of colored smithsonite I am finding that the link may be a combination of these factors and/or some contributing element(s). Unfortunately, studies of smithsonite are very uncommon. The universe of people studying this can probably be counted on the fingers of one or two hands.

30th Nov 2016 21:05 UTCBill Dameron 🌟 Expert

Jim is correct, I think. I have 95 smithsonite pictures in my gallery, and all are described as "Smithsonite." The attempt to add descriptive prefixes so common among many dealers who should know better just misleads. As Virgil has pointed out, yellow does not necessarily mean cadmium, cobalt pink, etc. Unless you have tested your specimen, it is smithsonite. And if you would like to be somewhat scientific, the proper IMA name is still "Smithsonite," not with any adjective in front. Color in minerals is far to complex for such gimmicks.

1st Dec 2016 01:26 UTCDoug Daniels

I have the following copied from a New Mexico Mineral Symposium Abstract from a while back. Thought I had a link to the article itself, but can't find it now.

THE COLORS OF SMITHSONITE: A MICROCHEMICAL INVESTIGATION

Patricia L. Frisch, Virgil W. Lueth and Paul F. Hlava

We analyzed four smithsonite (ZnCO3) samples with electron microprobes in an attempt to decipher the origins of the different colors. We examined samples that were blue green (Kelly mine, New Mexico), yellow (Hanover, New Mexico), blue purple pink with white bands (Sinaloa, Mexico), and green yellow (79 mine, Arizona). Previous authors have proposed, with some geochemical evidence, that the green color of smithsonite is due to copper, the yellow to cadmium, and the blue to cobalt. However, until now, no one has used modern microchemical studies to investigate the chromophores in smithsonite.

The Kelly mine sample exhibits strong color banding that corresponds to a change in solid solution of copper carbonate (CuCO3) in the smithsonite, with higher CuCO3 contents (as much as 3.0 wt %) occurring in the strongly colored green bands. No mineral inclusions occur in this sample, and there is little variation of the other minor elements present (calcium and lead). Therefore we believe that copper is the coloring agent in the green smithsonite from the Kelly mine.

"Cadmian" smithsonite from the Hanover mine contains inclusions of pyrite (FeS2) —300 μm on a side, iron-rich sphalerite or [(Zn,Fe)S], and either hexagonal greenockite or isometric hawleyite (CdS). The CdS occurs in brightly colored bands, which are —10 μm thick and contain about 17 % of these —1 pm diameter inclusions. In addition, as much as 19.5 wt % iron carbonate (FeCO3) is present in solid solution. From this evidence we hypothesize that both CdS inclusions and iron in solid solution are the coloring agents in yellow smithsonite from this mine.

The blue-purple-pink smithsonite sample from Sinaloa, Mexico, contains copper and cadmium but no cobalt! In addition to our work, others have found that pink "cobaltian" smithsonite lacks cobalt. Thus, the term "cobaltian" smithsonite should be abandoned. Line scans across the color zones show that CuCO3 is high in the purple-pink regions (1.5 wt %) and even higher (3.0 wt %) in the blue zones. Solid solution cadmium carbonate (CdCO3) concentrations are fairly uniform from 1.0 to 1.5 wt % in both blue and purple zones of the mineral. The coloring agents in this sample appear to be copper and cadmium but because CdCO3 is colorless, the cadmium is not coloring the smithsonite directly but it must be altering the way copper colors the mineral. Where the copper concentration is highest, the smithsonite is blue instead of green. As the concentration of copper gets lower, the color goes to purple pink in the presence of cadmium. The white zones are due to abundant inclusions of hemimorphite.

The green smithsonite from the 79 mine contains inclusions of hemimorphite, aurichalcite, a manganese and copper oxide, and CuCO3 and manganese carbonate (MnCO3) in solid solution. The inclusions are as much as 1 mm in size and are present mainly at the edges of the material. CuCO3 and MnCO3 have the greatest concentrations (as much as 1.7 and 2.0 wt %, respectively) of solid solution impurities and the strongest variation. The copper concentration is not as high as in the blue-green smithsonite from the Kelly material. The combination of lower amounts of copper and the presence of manganese may therefore account for the lighter green and yellow color of this smithsonite sample.

Acknowledgments

Part of this work was supported by the U.S. Department of Energy under Contract DE-AC04- 94AL85000. Sandia is a multiprogram laboratory operated by the Sandia Corporation, a Lockheed Martin Company, for the U.S. Department of Energy.

Dr. Nelia Dunbar and Lynn Heizler (New Mexico Bureau of Geology and Mineral Resources) assisted with the electron microprobe analysis. The Cameca SX-100 electron microprobe at the New Mexico Institute of Mining and Technology was partially funded by the National Science Foundation, Grant STI-9413900.

pp. 4-5

________________________________________

23rd Annual New Mexico Mineral Symposium

November 9-10, 2002, Socorro, NM

12th Dec 2016 21:05 UTCRalph S Bottrill 🌟 Manager

Thanks Doug, thats really a interesting study and illustrates the problem of linking colours to chemistry - not easy!

12th Dec 2016 23:39 UTCDebbie Woolf Manager

Very interesting reading, thanks.

12th Dec 2016 23:54 UTCRichard Gunter Expert

If Cd, Mn and Fe colour the Smithsonite , especially as inclusions, why is the accompanying Hemimorphite almost always colourless? Blue botryoidal Hemimorphite is found in the 79 Mine but as far as I know never with the green Smithsonite.

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