winchite-richterite?

Thought I would start a new thread on this. The issue has come up on two different threads as a secondary topic thus far. The question I have is all the winchite from afghanistan actually richterite?

They have been also labeled as Potassic-fluorrichterite. I believe it's the same material.

Maybe I need to ask this differently, or maybe this should be on the mistakes and errors thread, but has any confirmed winchite been found in Afghanistan? There are three photos on Mindat of white winchite from Afghanistan, however I can not imagine how they could have a pale blue-grey streak which according to Mindat winchite is supposed to have?

If you're concerned just label it as 'amphibole'. I think your first question "is all the winchite from afghanistan actually richterite" is one that cannot be answered. Individual specimens may be different, even from the same locality.

I haven't done any research to look up analysis of these amphiboles - but it might be worth checking out gemmology publications as well as mineral publications for references to winchite in afghanistan.

Jolyon

Hello Jolyon,

Thanks for the suggestion I have started a search. One interesting thing that came up right away was a paper in American Mineralogist ( [www.minsocam.org] ) that says that winchite from the type locality is not winchite rather Magnesio-arfedsonite or riebeckite! This reference is not in the Mindat database, maybe it should be?
However, it seems it was rediscovered at the type locality in 1986 (Min.Mag.V50, 173-175) but I don't have a copy of that paper. But it does raise the question as to where or not the photos of winchite from the type locality in Mindat are winchite or not. Can someone send me a digital copy of the Min.Mag. article?



Edited 1 time(s). Last edit at 05/27/2010 04:06PM by Reiner Mielke.

Bahahahahah.....deleting against the grain comments again, there's something new.

Now Craig give Jolyon a break, that is not the way it was.

My concern is that if improperly identified photos are put up on mindat it will give credibility to other similiarly misidentified samples and result in a "snowball effect". I have a sample of the colorless Afghan "winchite" ( so labeled by the seller). It does look like some of the photos on Mindat, so (based on an inadequate knowledge of the type material), it would be reasonable for me to assume that the label is correct. I might even post a picture of my sample on Mindat calling it winchite which would give all the previous photos even more credibility. I am sure that other collectors do the same thing, so it is very important to be reasonably sure of the identity of photos posted on Mindat. By reasonably sure, I mean at least match the essential characteristics of the type material. Correct me if I'm wrong, but isn't the streak one of these characteristics?

I think Lefteris nailed Potassic-fluorrichterite, but I haven't gotten around to checking it. I believe that is what Frank Hawthorne found for the Afghan yellow gemmy xls. The Amphiboles are real sods to sort out and I doubt that streak would do it. I'll check this and then go after the photos. I've been meaning to do that for over a year now. Sorry.

Thanks Rob.



Edited 1 time(s). Last edit at 05/28/2010 06:54PM by Reiner Mielke.

There must be several thousand photos to "sort out" on mindat. A lot of them very obvious and embarrassing. I just got through cleaning up a lot of images of agate nodules from Rio Grande do Sul that a frequent former contributor to mindat had given the locality of Minas Gerais to. Must have been 50 or more images. Then there were all the Rio Grande do Sul amethysts and citrine (burned amethyst) that had been labeled as being from Minas Gerais and a number of Rutile in Quartz listed as Minas Gerais that were from Bahia, etc etc. Sometimes I think we will never get it all cleaned up. But I think we now have a couple of good old fashion junk yard dogs now guarding the image input and if they keep up the good work it will give us some time to clean up the mess we already have.

Rock Currier
Crystals not pistols.

Further to the winchite question.
The amphiboles from the Isle of Skye epigranites are a real nightmare to assign to a specific species, and are probably imposable to do so. Many are zoned from ferrowinchite- ferroactinloite-ferroedenite-ferrorichterite-katphorite-riebeckite. I am in the process of writing an article on the miralitic epigranites of the Isle of Skye. I will probably lump these under the amphibole heading.
I hope you come up with a solution you can live with Reiner

All the best
Steve Rust

It is currently study a Monte Somma (Napoli, Campania, Italy) an amphibole was found to be a crystal mixture of winchite and richterite

Massimo

One would have thought that someone analyzed some of this stuff to come up with a name. I guess we just haven't heard from that person yet.

Anyone who has done single xl and WDS knows what that specimen is. The question then arises as to the homogeneity of the deposit and a few analyses are required for this. I suspect the Afghan amphiboles will show the same kind of variability as the Grenville ones do. Kocha valley is far bigger than Kipiwa and the locality info isn't yet nearly as good. In particular at Kipawa, the GSC in the early 90's said the amphibole was either Richterite or Potassian Magnesiokutaphorite depending on the analysis. At Mindat we have Magnesiokutaphorite (refernce is Mineralogical Research who were exchanging with the GSC at the time) and Magnesioferrikutaphorite, a discontinued amphibole, but with more Fe than Al in Magnesiokutaphorite. John Sobolewski posted this photo and gives himself as the reference.

That's why i don't collect amphiboles!:P Although I have two of these Afghani ones, one labeled Winchite and one Potassic-fluorrichterite....go figure!

Lefteris.

Its a surprising colour for any sodic amphibole - I know you cannot trust colours but having been working intermittently on various rocks with sodic amphiboles, usually messy mixtures of barroisite, winchite, glaucophane, riebeckite, magnesiohornblende, etc (sometimes several in one crystal!), and they are always iron and titanium rich so are usually dark colours: mostly black to dark blue or green. I dont know the Koksha geology but it must be an unusual chemical setting to get a colourless one, but the area does seem to have very Na-Al-rich Fe-poor rocks (sodic skarns?). But the point is amphiboles can be extremely variable within a single crystal let alone throughout a large area, so are almost impossible to name in some cases.
Rob: winchite can theoretically be Fe-free, but should have abundant Al; I presume Mg was also abundant?

Regards,
Ralph

Earlier I posted about one of the yellow gemmy bladed amphiboles for which I had an EDS. I screwed up badly on the peaks. Here's what I got arranged by peak height:
Si >> Al > Mg > Ca >> K > Na > Ti

So this might be a potassian winchite. At this point I think it hopeless to unambiguously assign any species to the amphiboles without single xl and WDS for that piece. Even then there could be mixed xls.

Hello Lefteris,

All you need now is one more from there, [www.mindat.org], and you will have all your "bases" covered. Out of the three at least one will turn out correct.(:D

Rob
That analysis could be any of these three amphiboles; a microprobe analysis would tell.

Regards,
Ralph

Thanks Ralf. That's from an energy dispersive spectrum (EDS), but what is needed is the finer width dispersive spectrum (WDS) with standards to get the chemistry quantitative and single xl work to place the atoms. EDS is often effective for metallic ores but not so illuminating for rock forming silicates.