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Mineralogical Classification"grandfather" status

4th May 2006 11:38 UTCChris Stanley

I was asked about so-called "grandfather" status early today and my first recollection of the term is in Nickel and Nichols (1991) where they define it as: "minerals introduced before the formation of the CNMMN and generally accepted by the mineralogical community".

Three questions: 1. Anyone know of an earlier usage of the term in this context?

2. Can it be applied to a mineral that was once accepted then fell into disuse, and which now seems to have been resurrected?

3. Which mineral do you think I have in mind?

4th May 2006 12:09 UTCPeter Haas

(1): I have no idea

(2): No. "Resurrection" (when I get you right) implies a re-definition. The mineral then would be listed as "re-defined", not as "grandfathered" - no matter what the status of the name was before the re-definition.

(3): Again, no idea. (The first mineral that came to my mind when I did read your post was Aspidolite).

pH

4th May 2006 12:42 UTCErnst A.J. Burke

The origin and further history of the 'grandfather' status of mineral species was described by Jeffrey de Fourestier in his 2002 paper (Can. Mineral., 40, 1721-1735) on the history of the CNMMN.

4th May 2006 14:11 UTCAlfredo Petrov Manager

Some collectors and list compilers are under the mistaken impression that "grandfathering" means that ANY mineral described pre-IMA remains an "official" species forever, unless specifically discredited, ignoring the part about "... and generally accepted by the mineralogical community". If some nonsense was described before 1959, and doubts have frequently been expressed about its legitimacy, it fails this test and shouldn't be considered "grandfathered". Nevertheless, some species collectors still have dubious things on their 'want lists' just because "The IMA hasn't discredited it"!

4th May 2006 16:44 UTCJim Ferraiolo

The correct term for Chris's (2) would be 'revalidation'. "A mineral that has been discredited or fallen into disuse may be revalidated if a re-examination shows that the mineral meets the normal criteria for a distinct species or that it is a mixture containing a new mineral species. Requirements for revalidating... are similar to those for redefinition."

'Redefinition' of a species that requires approval by the CNMMN if redefinition of the mineral is "(a) on structural grounds, (b) by adding or deleting one or more chemical components regarded as essential to the definition, or (c) by proposing compositional limits in a solid-solution series that are not compatible with the existing definition of the 50% rule (or its equivalent in multicomponent systems". "Redefinition .. requires a review of the literature on the mineral to be redefined, a re-examination of the type specimen, a comparison of the new data with the original, and a justification for the redefinition"

The Guidelines also state a redefinition does not have to be approved by the CNMMN "are those resulting from structural refinements or new chemical knowledge..."

A question comes to mind. At first reading, redefinitions based on structural refinements seem to be require AND not require to be approved by the CNMMN. Yes or no? If yes, at what point?

8th May 2006 17:20 UTCChris Stanley

Thanks to all of you who replied with useful information. 'palladinite' is the mineral I had in mind.

8th May 2006 19:17 UTCErnst A.J. Burke

Years ago I have asked Jacques Jedwab to submit to the CNMMN a proposal to revalidate palladinite as a valid mineral phase, but for some reason he does not believe in the CNMMN ...

8th May 2006 21:05 UTCAlfredo Petrov Manager

Apart from palladinite, are there any other known occurences of natural PGM oxides? I recently found a grain from British Columbia that shows only Pt and O. I'm tempted to ascribe this to some sort of machine error, but the grains probed 4 minutes before and 4 minutes after both showed just common Pt-Fe. I'll have it done again, since it wasn't something I expected to find in nature, but "palladinite" has made me more curious about it.

9th May 2006 01:25 UTCJim Ferraiolo

Alfredo,

A quick list of what I've turned up. Haven't checked if I have all the references.

Palladium oxides have ben reported from:

1. Caue iron mine, Quadrilatero Ferrifero, Itabira dist. Brazil - Econ. Geol. 90,118-134(1995); Min.Mag. 59,455-463 (1995); Can.Min. 34,547-557(1996); Min. Mag. 66,327-336(2002)

2. Lavatrafo, w. Andriamena, Madagascar - Min.Mag. 63,345-352(1999)

3. Gongo Soco,Quadrilatero Ferrifero, Minas Gerais, Brazil - Min. Mag. 65,169-179(2001); Can. Min. 41,473-478(2003); Min. Mag. 67, 453-463(2003)

4. Chudnoe, near-Polar Urals - Doklady, Earth Sci. Section 40091),109-112(2005)

5. Eastern Bushveld complex, South Africa - Can.Min.43,1711-1734(2005)

6. Serra pelada Au-Pd-Pt deposit, Carajas Mineral Province, n. Brazil - Econ. Geol. 97,1127-1138(2002)

9th May 2006 05:39 UTCAlfredo Petrov Manager

Thank you very much, Jim.

I wonder how stable Pd oxide is in a surface environment?

A chemist told me that Pt oxide, in contrast, would be so unstable as to be explosive.

9th May 2006 09:13 UTCPeter Haas

"A chemist told me that Pt oxide, in contrast, would be so unstable as to be explosive."

Think logical. This would mean that Pt4+ readily oxidizes O2-. What would happen, consequently, with a compound of Pt and a less electronegative non-metal, such as PtAs2 (sperrylite) ?

9th May 2006 15:16 UTCJim Ferraiolo

Jedwab in his "Bibliographic Guide to unconventional platinum group minerals and mineraloids (UPGMM)" references Pt₃O₂ and Pt₂O₃ from Burma (Weiser,1992 - Abstr. 6th Intl Platinum Symposium in perth, 52, p52 (1990); PtO, PtO₂, Pt(OH)₂ and PtO.H₂O from S. Africa (MacDonald et al., S.Afr. J. Geol. 102(3),184-191(1999). The 'Guide' is available at Dr. Jedwab's website.

9th May 2006 15:28 UTCFrank

Re: think logical.

I agree PtO2 exists as a phase, however some things are not quite as trivial as expressed by the 'think logical':

According to the "logic" expressed above FeAs2 should not be stable as FeO2 is not exactly a common compound...

9th May 2006 16:14 UTCPeter Haas

"According to the "logic" expressed above FeAs2 should not be stable as FeO2 is not exactly a common compound ..."

If you understand the logics, you won't compare FeAs2 (a Fe2+ compound) and FeO2 (an entirely hypothetical Fe4+ compound). Supposing that PtO2 is not stable implies to be concerned about the ease with which Pt4+ can be reduced to the element. Consequently, I refer to the tendency of Pt4+ to oxidize the anion. The platinum cannot get further oxidized, which facilitates the problem (in particular, I won't have to be concerned about homoeopolar bonds in the anion). It is the oxidation state of the metal that matters here, not the stoichiometry of the compound. Incidentally, the Pt(IV) arsenide (covalent As-As bond in the As2(4-) ion) and the Pt(IV) oxide have the same stoichiometry.

Keeping on thinking logical does not mean to switch off any chemical knowledge. My statement does not apply to iron(II) compounds, because Fe2+ is not easily reduced, but easily oxidized.

17th May 2006 09:18 UTCjacques jedwab

1. Actually, the palladinite case has been re-submitted to IMA about 10 years ago with A. Criddle and a handful of distinguished gentlemen, but a reviewer demanded a single-crystal structure, which was impossible for an obviously polycrystalline material. "Obvious" did not seem an excuse, and I gave up.

2. For all those who still wonder about the existence and stability of oxidic PGM, I have gathered my own bibl. references, the historical references (since 1711), and several original pictures at URL's to be found here: http://www.ulb.ac.be/sciences/dste/volcano/JJ/JJ.html

Special emphasis has been put there on Katanga and on Urals (irite). Several personal observations of UPGM in noteworthy deposits (Stillwater, Br. Hill, Alaska, Nevada, California) are in my files and their publishing on the web will hopefully materialize.

3. To the happy few who care (and are not afraid of sitting for hours at the SEM-desk) I am glad to tell that a rare Pd-Ag-Cu-I-(O?) occurs at Broken Hill, NSW. The would-be gun(wo)man should be warned that the mineral is quite volatile under the e-beam.

J.J.

17th May 2006 09:27 UTCjacques jedwab

For some unknown reason, the announced URL did not show up in my former message:

http://www.ulb.ac.be/sciences/dste/volcano/JJ/JJ.html

Soory, J.J.

17th May 2006 09:30 UTCjacques Jedwab

I did not grasp something. Perhaps time for reading instructions? Hope this will work:

www.ulb.ac.be/sciences/dste/volcano/JJ/JJ.html

J.J.

17th May 2006 12:04 UTCErnst A.J. Burke

I think there is a misunderstanding somewhere. Palladinite was not submitted for redefinition or other status to the CNMMN (at least there is nothing in the CNMMN archives), but a manuscript on the mineral was submitted to Eur. J. Mineral., and there it was stated that more study was needed, and there were problems with the chemistry, as far as I recall. But Jacques Jedwab will have the precise details.

Minerals are regularly approved by the CNMMN wthout a single-crystal study.

19th May 2006 14:21 UTCChris Stanley

Hello everyone,

Thanks to all of you for your interest.

I pulled out the (very thick) file from one of Criddles filing cabinets in my office and found that indeed a draft proposal was sent to the commission in 1996 but it was for a redefinition.

Maybe a revalidation is different and might meet with a more positive response than was received in the memo from Ernie Nickel of 4 November 1996 and which seemed to put a dampener on the whole project.

22nd May 2006 13:34 UTCDavid Von Bargen Manager

Jacques,

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