New minerals 2012 approved by IMA CNMNC - February-May 2012

2 member series are are just a way of describing solid solutions. Until I was caught by the pedantry of 2 members, I and everyone I talked to understood that solid solution series described the full set of 2 member series that describe the solid solution. Don't worry about it Alfredo, leave the 2 member series to the dimesionly challenged pedants and speak freely about solid solution SERIES with several end members.

Uwe Kolitsch Wrote:
-------------------------------------------------------
> IMA No. 2011-100
> Forêtite
> Cu2Al2(AsO4)(OH,O,H2O)6
>
> is the former "Unnamed (Cu-Al Arsenate)"
> [www.mindat.org]

Other confirmed locality at Salsigne.

[For tellurocanfieldite] I would have suggested "member of the Argyrodite group" (2.BA.35 in Nickel-Strunz 10).



Edited 1 time(s). Last edit at 06/26/2012 12:29PM by Jim Ferraiolo.

IMA No. 2012-013
Tellurocanfieldite
Ag8SnTe2S4
Bajiazi lead-zinc deposit, Jianchang County,
Liaoning Province, China (40º35’30’’N 120º02’16’’E)
Gu Xiangping*, Xie Xiande, Lu Anhuai, Kenich
Hoshino, Huang Jiwu and Li Jielan
*E-mail: guxp2004@163.com
Argyrodite-canfieldite series
Orthorhombic: Pna21
a = 15.615(4), b = 7.803(3), c = 11.043(7) A ˚
6.373(21), 3.330(28), 3.186(85), 2.759(49),
2.253(100), 2.124(71), 1.951(51), 1.865(27)
Type material is deposited in the collections of
the Geological Museum of China, Beijing
People’s Republic of China, catalogue number
M111801
How to cite: Gu, X., Xie, X., Lu, A., Hoshino, H.,
Huang, J. and Li, J. (2012) Tellurocanfieldite,
IMA 2012-013. CNMNC Newsletter No. 13,
June 2012, page 816; Mineralogical Magazine,
76, 807-817.

Given the information in the above note the crystal structure of "tellurocanfieldite" it would not be resolved. The words "structure determined" are not in the text.
I call the attention to the fact that Bindi et al. (2012) have recently presented a paper on Te-rich canfieldite from Lengenbach.
Here is the abstract.
The study with SCXRD performed by Bindi et al. (2012) on the sample from Lengenbach, with nearly identical chemical composition, shows that the Te atoms are disordered in the relevant five structural sites (none of them predominates in tellurium), and the phase, as demonstrated by several tests, is cubic and not orthorhombic.
Not having been observed as reported by Chinese authors in the proposal (check list) I do not have all the elements for a good judgment, but I would say that the proposal and approval deserve a reassessment in order to well understand if the compound has indeed all the qualifications to be recognized as a new mineral species.

Reference:
▪ Bindi, L., Nestola, F., Guastoni, A., Zorzi, F., Peruzzo, L., Raber, T. (2012): Tellurian canfieldite, Ag8Sn(S,Te)6, from Lengenbach quarry, Binntal, Canton Valais, Switzerland: occurrence, description and crystal structure. Canadian Mineralogist, 50, 111-118.

Abstract:
In order to evaluate the effects of Te-for-S substitution in the minerals of the argyrodite group, the crystal structure and chemical composition of a crystal of Te-rich canfieldite from the Lengenbach quarry, Binntal, Switzerland, was investigated. The unit-cell parameters are a 11.0003(6) Å and V 1331.1(1) Å3. The structure was solved and refined in the space group F4-3m to R1 = 0.0308 for 194 independent reflections and 21 parameters. Quantitative analysis led to the chemical formula Ag8.05(Sn1.03Ge0.01)∑1.04(S3.95Te1.95Se0.01)∑5.91, ideally Ag8Sn(S,Te)6. The crystal structure of Te-rich canfieldite was found to be topologically identical to that of putzite, (Cu4.7Ag3.3)GeS6. Neglecting the short Ag-Ag contacts (due to disorder), the two Ag atoms in the structure can be considered as three-fold (Ag1) and four-fold (Ag2) coordinated. Tin adopts a regular tetrahedral coordination. The refinement of the site-occupancy factor indicates Te to be disordered over the three anion positions (i.e., X1, X2, and X3), with a preference for the X1 site.



Edited 1 time(s). Last edit at 06/28/2012 09:56AM by Marco E. Ciriotti.

Sorry I missed the "orthorhombic" in tellurocanfieldite/ Thanks Marco. It clearly not in solution series, multidimensional or not!!!

Dear Sir,

I wonder if you can help me. I have been trying to get a a PDF copy of the paper relating to the silica mineral chibaite by Momma et al (2011). The web listed e-mails do not work on my computer.

Best regards,

John Betterton (Museum Geologist)

You can send an email to the first author, see bottom of [www.nature.com]

John,
A copy is on its way.

The chemical formula for Fuettererite, as listed in the IMA CNMNC proprosal by Marco Ciriotti, is incorrect. Tony Kampf has corrected it on the Fuettererite mineral page. The correct formula is Pb3Cu6TeO6(OH)7Cl5.

Thank you, Brent.

Perhaps I should have added that tyrolite is not orthorhombic and it makes no sense to rename it clinotyrolite. The mineral that was known as clinotyrolite has a different chemistry and structure. Clino-enstatite is a polymorph (ie chemically the same) with only the crystal structure being different.

Re: Tellurocanfieldite:

Tellurium-rich canfieldite has been long known from Bajiazi (Li, Y. and Qing, C.K. (1999): Acta Mineralogica Sinica 19, 426-435), which is now also the TL of tellurocanfieldite. If we disregard the possibility that it is in fact a variety and not a new mineral, the formula with "Te₂S₄" suggests that there either are two different anion sites or there is a phase transition (structural change) occurring with increasing tellurium content in canfieldite. Both observations imply that there was at least some preliminary structure research carried out.

2012 MINERAL APPROVAL WITHDRAWN

IMA No. 2012-013 Tellurocanfieldite
Approval for this mineral has been withdrawn
(Gu, X., Xie, X., Lu, A., Hoshino, H., Huang, J.
and Li, J. (2012) Tellurocanfieldite, IMA 2012-
013. CNMNC Newsletter No. 13, June 2012,
page 816; Mineralogical Magazine, 76,
807_817). A subsequent single-crystal structural
analysis has shown that Te is disordered
over the three sulfur sites and thus the material
is in fact Te-rich canfieldite.

"Fuxiaotuite appears to be the same as "clinotyrolite" which was published without approval and later considered as invalid. Also note that the TLs given for Fuxiaotuite are the same as those previously specified for clinotyrolite."

"It is the same mineral as "clinotyrolite" but as all tyrolite is monoclinic and this mineral is definitely not tyrolite the name change was approved in the IMA accepted proposal."


In fact, the space group is identical with and the unit-cell parameters are very close to those of the 2M-polytype of tyrolite (C2/c; a = 54.520(6), b = 5.5638(6), c = 10.4647(10) Å, beta = 96.432(9)°; Krivovichev et al., 2006). [have added this comment to the fuxiaotuite page]
I first thought: shouldn't fuxiaotuite be just considered a polytype of tyrolite and therefore discredited?
Then I noticed that tyrolite is defined as a SO4-free, but CO3-bearing species, and fuxiaotuite as a SO4-bearing, but CO3-free species. I am really looking forward to see the crystal structure and how its details were determined.