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Identity HelpDickinsonite - Chandlers Mill mine

13th Jul 2014 19:28 UTCPeter Tarassoff Expert

I note that dickinsonite has been crossed out on the list of minerals from the Chandlers Mill mine, supposedly because of "erroneous literature entries." I have a dickinsonite specimen that was collected by Gunnar Bjareby in 1957. I also have dickinsonite that I personally collected in 1958. Both have been verified by X-ray diffraction. Can anybody out there who is familiar with the locality please comment?

Peter Tarassoff

13th Jul 2014 23:20 UTCPeter Tarassoff Expert

-- moved topic --

14th Jul 2014 00:29 UTCVandall Thomas King Manager

Dear Peter,

The traditional identification was "dickinsonite". Paul Moore chemically analyzed these and determined they were the iron-analog arrojadite.

Best Wishes, Van

9th Sep 2014 19:01 UTCRobert Wilken

Hi Peter,

Long time since seeing you at MSH! Anna and I acquired a few of Marcelle Weber's NH "pencil boxes". Among them was one G E Smith box dated 7/16/71 that had only two minerals listed on it: brazilianite and dickinsonite. There was one narrow 5 cm long massive piece mostly made up of a resinous, highly fractured dark green to pale yellowish material. I can only think that Morrill's NH guide steered people to dickinsonite as the likely mineral back in that day.

Since I'm set up for micros, my photo is a closeup with about a 10 mm fov. When I sent the photo to Tom Mortimer (MindatNH.org) he replied with a link to his website "Arrojadite Gallery." You will see there a photo of a Harvard specimen ID'd as arrojadite from Chandlers Mill Mine. It looks very much like the M W-collected piece . Nevertheless, I will send a shard for an EDS at some point and will post the result here.

Bob Wilken

Campton, NH.

10th Sep 2014 01:29 UTCVandall Thomas King Manager

Harvard professors and students were studying the phosphates in the early 1950s. The specimens were easier to x-ray than to chemically analyize and many New England phosphates were identified this way. However, the students such as Mary Mrose and Marie Louise Lindberg (eventually Smith) named specimens according to best match of x-ray lines and not by chemistry. Many of the identifications were of Mn-rich equivalents of actually Fe-rich specimen. The errors were discovered until the 1960s through the 1980s, although there continue to be re-identifications made. When Morrill published his guidebooks, the identifications he reported were those of the early students who only x-rayed the specimens.

11th Sep 2014 18:45 UTCTom Mortimer Expert

Hi Van,

On your July 13 post you stated: " Paul Moore chemically analyzed these and determined they were the iron-analog arrojadite."

By "these" do specifically mean Chandlers Mill specimens? I could find no mention in Moore et. al.'s 1981 American Mineralogist paper to analyses of Chandler Mills specimens. Perhaps Moore's chemical analyses were published elsewhere?

I note Encyclopedia of Minerals (2nd edition) lists arrojadeite as "small cleavable masses in pegmatite at the Smith Mine, Chandlers Mill, Newport " and lists Moore's 1981 Am. Min. article as the most recent reference.

Tom Mortimer

12th Sep 2014 01:46 UTCPeter Tarassoff Expert

Hi all,

Interesting. On the Bjareby specimen I have, there is a nodule consisting of a central phase with a dark green color exactly like Bob's Weber specimen, surrounded by a lighter greenish-yellow phase which may be an alteration product. The material I collected also has two phases.

Regards.

Peter

(Bob, nice to hear from you.)

12th Sep 2014 16:05 UTCVandall Thomas King Manager

Paul told me about his work on Palermo arrojadite and that he examined a number of additional specimens including the Newport occurrence. You should find the data in : Moore, P. B. and Ito, J. (1979) Alluaudites, Wyllieites, Arrojadites: Crystal Chemistry and Nomenclature, Mineralogical Magazine, v. 43, p. 227-235. Also in Bideaux et al. v.4. There are data at: http://minerals.gps.caltech.edu/FILES/Visible/Arrojadite/Index.html. Ostensibly, the Smithsonian has an analyzed specimen: http://collections.si.edu/search/record/nmnhmineralsciences_1054789. The best review of the chemistry of the series I know of is: Chopin, Christian, Oberti, Roberta, and Camara, Fernando (2006) The Arrojadite Enigma: II. Compositional Space, New Members, and Nomenclature of the Group, American Mineralogist, v. 91, p. 1260-1270. They include the previously cited chemical analyses.

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