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Improving Mindat.orgAnkerite with no proof
11th Feb 2018 11:10 UTCReiner Mielke Expert
11th Feb 2018 15:58 UTCUwe Kolitsch Manager
11th Feb 2018 16:57 UTCVik Vanrusselt Expert
I got the ID from the label.
Nevertheless, I have changed the ID to Dolomite.
1) How would one test this specimen to distinguish ankerite from dolomite?
2) How come https://www.mindat.org/photo-855026.html is ankerite "without proof" when my specimen isn't?
Vik
11th Feb 2018 17:28 UTCJolyon Ralph Founder
Just chance that yours was seen first, that's all.
11th Feb 2018 17:32 UTCVik Vanrusselt Expert
Any idea on how to test for the distinction between ankerite and dolomite? Something to do with the iron content?
Vik
11th Feb 2018 17:34 UTCUwe Kolitsch Manager
Messagen sent on 855026.
11th Feb 2018 17:45 UTCReiner Mielke Expert
EDS would tell you. Unfortunately there are lots of other unproven ankerites not to mention hundreds of other minerals. I have brought this up before and management does not want to go back and change things as this would require a lot of work. Real ankerite is very rare and one has to start somewhere. However if you think it is ankerite then it would be worth testing.
I'm still looking for a piece of ankerite for my collection even though the local gold mines all report that they have ankerite. There is even a townsite and mine called Ankerite but all they have is ferroan dolomite. It is common among geologists to call any iron bearing dolomite ankerite even though it does not contain enough iron to be a true ankerite. Which reminds me I have to send some samples off next week to see if they are ankerite. "Fingers crossed."
11th Feb 2018 18:40 UTCFranz Bernhard Expert
Styrian Erzberg has plenty of real ankerite (At. Fe > At. Mg). Should be easy to get a sample from Austrian collectors.
Hope you are lucky with your tests. You know, if At. Fe is close to At. Mg, qualitative EDS will not work, quantitative analyses will be necessary.
Franz Bernhard
11th Feb 2018 19:17 UTCChristian Auer 🌟 Expert
Ankerite status: Erroneously Reported !
I`m quite sure you had enough real and analysed ankerite from there in your hands - as did I!
11th Feb 2018 20:07 UTCUwe Kolitsch Manager
has electron microprobe analyses showing that ankerite (Fe>Mg) occurs.
Page updated. (The ref. was also missing in the list.]
PS Chris: have sent you the PDF.
11th Feb 2018 22:22 UTCMark Heintzelman 🌟 Expert
Yes, by it's modern definition in attempts to add consistent rules in determining boundaries in solid solution series, ankerite has now become a virtually theoretical mineral species, very rarely found in nature. Despite not wishing to pursue the efforts involved, all current ankerite localities and images in the galleries really do merit being moved to Ankerite-Dolomite series until proven by a full analysis, for sake of accuracy and due to it's actual rarity in nature.
I certainly appreciate Renier taking up this quest for accuracy . . . death by a thousand cuts, if it must be done that way. (thanks).
ANKERITE-DOLOMITE (Styrian Erzberg, Eisenerz, Styria, Austria) 10.8 x 5.2 x 3.0 cm
MRH
11th Feb 2018 22:29 UTCVik Vanrusselt Expert
is that only 1 (one!) of them actually has a SEM-EDS result in the caption, namely this one: https://www.mindat.org/photo-722902.html
Therefore, I concur with Mark Heinzelman's comment to rename all "ankerite" photos on Mindat to "ankerite-dolomite series", unless sufficient analysis results are available.
Vik
12th Feb 2018 03:04 UTCRalph S Bottrill 🌟 Manager
Ankerite is not incredibly rare, I commonly find when analysing dolomites that some crystal zones have Fe>Mg, but Mg overall nearly always dominates so it’s a stretch to call the whole specimens Ankerite.
12th Feb 2018 05:21 UTCKeith Compton 🌟 Manager
12th Feb 2018 06:19 UTCFranz Bernhard Expert
https://www.mindat.org/loc-57910.html
to back up Ralphs statement.
BSE-images of polished sections, field of view 0.46 mm and 0.31 mm, respectively.
Both from sample AN801.
And a triangular Fe-Mg-Mn diagramm of these minerals.
Franz Bernhard
12th Feb 2018 06:44 UTCFranz Bernhard Expert
A diagram with carbonate rock analyses from the Styrian Erzberg in a paper from 1973, Beran´s work is already mentioned.
The green line is At. Fe : At. Mg 1:1
The red line is ideal stoichiometric dolomit-ankerite series.
It shows clearly that there are "dolomite rocks" and "ankerite rocks" at the Styrian Erzberg.
But this does nothing say about the nice, nearly white rhombohederal crystals...
Franz Bernhard
12th Feb 2018 06:56 UTCChristian Auer 🌟 Expert
By the way, what is the white rim on your first BSE picture, galena?
12th Feb 2018 07:42 UTCAlfredo Petrov Manager
The reality is that both collectors and geologists use a lot of "field terms" that do not match modern species definitions, and I see nothing particularly heinous about that, as long as we keep in mind that that happens, and that the vast majority of specimens will never be analyzed, at least with the current state of technology. So yes, let's change all unanalyzed "ankerites" to Ankerite-Dolomite Series, even those from the Ankerite type locality (where Fe-rich dolomite seems to be at least as abundant as true ankerite), but at the same time I'd like to stress that labels saying "Ankerite", when they really mean Fe-rich dolomite, are not "errors", and we don't need to crticise the label writers, they just need redefinition.
12th Feb 2018 10:26 UTCPavel Kartashov Manager
-------------------------------------------------------
> Ankerite is not incredibly rare, I commonly find
> when analysing dolomites that some crystal zones
> have Fe>Mg, but Mg overall nearly always dominates
> so it’s a stretch to call the whole specimens
> Ankerite.
I can't to agree with Ralph here - too much samples labeled as "ankerites" shows low or negligible iron contents even in most enriched by it zones. They often aren't even "ferrodolomites" at all. Another usual case is when dark oxidized carbonate is composed by mixture of dolomite (low ferroan) and mixture of iron oxides. This is typical for localities of Nagol'nyi Kryazh - prolific sourse of "ankerite" samples in former USSR. However I saw similar "ankerites" and from Erzgebirge.
What about a diagram Mg-Fe-Mn, it is good and visual, BUT in case with ankerite it always necessarily must to be accompanied by Mg-Fe-Ca one, because of we have perfect solid solutions in system Mg[CO3]-Fe[CO3]-Mn[CO3] much more abundant and widespreaded in nature than Fe-rich minerals of dolomite-ankerite series. And part of "ankerites" from his Mg-Fe-Mn diagram quite able to stay on bottom side of tetrahedron Mg-Fe-Mn-Ca with Ca at top. ;-)
So Franz should to show us one more diagram for his samples AN1018 &AN1019 - for example Mg-(Fe+Mn)-Ca one.
From other hand, his the second diagram shows almost complete absence dolomie points on it, what is in contradiction with his the first diagram. :-\??
12th Feb 2018 12:12 UTCFranz Bernhard Expert
the rims around the siderite are "limonite".
Pavel,
the ankerites-dolomites from Kaltenegg and Wagnerhöhe are nearly stoichiometric Ca(Mg,Fe,Mn)(CO3)2, for this reason I didn´t made a diagram with Ca. Looking into the original data set, the ankerite-dolomite poorest in Ca has the composition:
Ca0.952(Fe0.460, Mg0.448, Mn0.140)(CO3)2
(concering all four quantitatively analyzed samples).
The second diagram from Styrian Erzberg has nothing do to with the first diagram from Prinzenkogel (Kaltenegg, Wagnerhöhe), its a totally different deposit.
Franz Bernhard
12th Feb 2018 12:53 UTCVik Vanrusselt Expert
https://www.mindat.org/photo-822665.html
https://www.mindat.org/photo-388537.html
https://www.mindat.org/photo-66907.html
https://www.mindat.org/photo-721758.html
Vik
12th Feb 2018 13:04 UTCFranz Bernhard Expert
Franz Bernhard
12th Feb 2018 13:23 UTCFranz Bernhard Expert
Franz Bernhard
12th Feb 2018 13:48 UTCReiner Mielke Expert
You should put that Styrian Erzbirge photo into the database as it is very informative. Have you ever found any euhedral crystals like that from there that were dolomite?
12th Feb 2018 13:56 UTCRonnie Van Dommelen 🌟 Manager
12th Feb 2018 14:03 UTCReiner Mielke Expert
12th Feb 2018 14:11 UTCFranz Bernhard Expert
sorry, photo and data not good enough for upload...
No, I have no confirmed euhedral dolomite from Styrian Erzberg, but I have checked only very few samples. But have a look at the post of Christian:
"Unfortunately colour is no good ID reason for those pale yellow-white rhombs from the Styrian Erzberg. I once ID 8 different species. Three were pure dolomite, one ankerite and the rest mixing up within a single xtl."
The story goes on...!
Franz Bernhard
12th Feb 2018 14:41 UTCPavel Kartashov Manager
please try to make better photo from this or similar sample. It is very important for the explanation to dumb collectors, that real fresh ankerite is colorless or white without brownish hue. This brownish coloration is often the "main diagnostic property" for ankerite determination. I simply tired to explain again and again this simple fact.
12th Feb 2018 14:52 UTCReiner Mielke Expert
I think you should make an exception for this photo and accept it into the database.
12th Feb 2018 14:54 UTCUwe Kolitsch Manager
12th Feb 2018 15:02 UTCFranz Bernhard Expert
sorry, I am unable to make a better photo!
If managers think this photo should be moved to the database, please feel free to do so!
Franz Bernhard
12th Feb 2018 15:14 UTCReiner Mielke Expert
12th Feb 2018 15:36 UTCAlfredo Petrov Manager
12th Feb 2018 15:48 UTCDavid Von Bargen Manager
Note: Most (unanalysed) "ankerite" specimens are actually Fe-bearing (ferroan) dolomite (Mg>Fe), because of nomenclature changes. The majority of alleged "ankerite" photos here actually depict Fe-rich dolomite (except for a relatively few analytically confirmed ankerites). Even the old so-called "type locality ankerite" from Erzberg, Styria, would not quite fit the modern definition, with analysis showing (Mg 0.520, Fe 0.457, Mn 0.021) apfu
12th Feb 2018 15:53 UTCReiner Mielke Expert
What you are proposing I think is too high a bar. I think we need to distinguish between absolutely confirmed and those that have supporting evidence confirming. If not then you would have to declare most of the minerals and photos in mindat as being unconfirmed. Maybe we need a partially confirmed category?
12th Feb 2018 15:55 UTCReiner Mielke Expert
12th Feb 2018 17:12 UTCPavel Kartashov Manager
12th Feb 2018 17:40 UTCReiner Mielke Expert
Can you see any reason why ankerite cannot be colorless and transparent like some dolomite crystals?
12th Feb 2018 18:16 UTCJeff Krueger
Regarding the recatagorizing/renaming of unconfirmed specimens, would it at least be possible/make sense for the select few photos/specimens in the Ankerite Gallery>Photos of Ankerite>Ankerite page be confirmed specimens? Right now the gallery contains many beautiful and, I suspect, unconfirmed photos of brown, Fe-bearing (ferroan) dolomite (Mg>Fe). This might be misleading.
I mention this because I often refer to the gallery images as a reference tool. By having mis-identified specimens in the gallery the problem of mis-attribution may be perpetuated.
12th Feb 2018 21:56 UTCRalph S Bottrill 🌟 Manager
I'm not sure that note is sufficient to counter the huge number of ankerite locations and photos added, and doubt most casual users would check?
I agree if we could automatically replace all ankerites with "dolomite-ankerite" it would be a lot more accurate, then we just need to find all the analytically confirmed ones.
I never meant to criticise anyone for using the name, its going to take a generation at least for geologists, average collectors and other people to stop using the name, and nobody expects all curators or collectors to relabel all their 100-year old, non-analysed specimens.
Pavel, maybe its rare in Russia, but I have confirmed it in a number of locations in Tasmania, using microprobe, or calibrated SEM-EDAX on polished sections, and not due to incusions. If you get assemblages with coexisting dolomite and siderite you can usually find some, but rarely in big homogeneous crystals.
Great data thanks Franz, it would be great to have this formally added to Mindat!
Maybe we need a partially confirmed category?
Interesting thought Reiner though some would suggested it is either confirmed or not and what would constitute partial confirmation: hardness, colour, habit? Re colours, I have seen kutnahorite grading into true ankerite (and dolomite) and the colour is a very pale pinkish cream.
12th Feb 2018 23:14 UTCReiner Mielke Expert
13th Feb 2018 00:29 UTCKrzysztof Andrzejewski
.....................................................................................................................................................................................................
- Alizarin red test
used by Huegi (1945) Friedman (1959) Warne (1962), Evamy (1963) Dickson (1965); I succesfully used version of Evamy, details:
Evamy B. D. - The application of a chemical staining technique to a study of dedolomitization.. Sedimentology 1963 vol. 2 no. 2.
Very useful solution in field research, very simply and cheap, could be quickly made in any chemistry laboratory. One drop on the mineral specimen and
calcite/aragonite without Fe2 + - turn red
calcite with a small amount of Fe2 + - turn pinkish purple
Fe-calcite - purple
dolomite without Fe2 + - clear
Fe dolomite - turn light blue
ankerite - turn dark blue
time of reaction - aprox. 1 minute and you have results. At home you keep bottle in cold & dark in kitchen fridge. Tested many times during the field trips to Nowa Ruda/Slupiec in Sudetes Mountains, Lower Silesia (Neurode/Schlegel in Schlesien), Poland, where ankerite and calcite are main carbonate minerals in hydrothermal veins in carboniferous series.
regards -
K.Andrzejewski
P.S. Colour of ankerite is absolutely not diagnostic.
13th Feb 2018 01:19 UTCReiner Mielke Expert
13th Feb 2018 02:40 UTCTed Hadley
Ted
13th Feb 2018 03:18 UTCMartin Rich Expert
@ Christian: I have some smaller samples like this one in the photo below. If you have time and interest, I can send you some for analysis.
13th Feb 2018 05:17 UTCAlfredo Petrov Manager
No, Reiner, I'm not trying to establish a high bar; quite the opposite - I'm appealing for more tolerance in naming when a mineral name also has a parallel "fuzzier" meaning (as in the cases of ankerite, piemontite, freibergite, numerous tourmalines and amphiboles, etc etc), or is traditionally used as a "field term", which is why I was pointing out how extremely difficult it would be to insist on 100% confirmation. Let's face reality: the vast majority of mineral specimens are never going to be analyzed. Even the ones that are "analyzed" are often insufficiently analyzed to determine the species (especially difficult ones like tourmalines and amphiboles). In such cases I think it's sufficient just to put a warning notice on the species page (as Mindat has already long had on the Ankerite page) explaining the complications involved. Admittedly just my personal bias; other Mindat members will probably want to be much stricter.
"Maybe we need a partially confirmed category?" That is pretty much the category that the majority of rare species photos in Mindat already fall under.
As for the comments about colour in ankerite, the only true ankerites I'm personally familiar with, the ones from the Cerro Sapo carbonatite in Bolivia, are light green! I see no reason why ankerites should be brownish (as most "ankerites" in collections are), unless partially weathered and oxidised. Pure Fe2+ salts are generally colorless.
13th Feb 2018 06:49 UTCFranz Bernhard Expert
Prinzenkogel data added.
Franz Bernhar
13th Feb 2018 09:15 UTCKrzysztof Andrzejewski
..............................................................................................................................................................................................................................................
- - so to distinguish TRUE dolomite from TRUE ankerite for example :) :) :)
In Poland every mineralogy student must have good ability to distinguish colors & shades but in this case, ankerite color is so deep (dark) blue, that with no doubt you can confirm this mineral. ONLY in other cases - when the sample turn light blue, you can start this discussion as above, so I would spare myself energy and exclude first all what is possible without wasting money.
About colours of ankerite - in Nowa Ruda I have found mostly milky ones rhombohedrons, turning yellowish or even brownish after lying for a while on dumps, but also sometimes very nice greenish (fresh after recovering) botryoidal forms. And with very similar mineralisation to Kladno in Czech Republic like on the mindat links added by Vik Vanrusselt above.
Before Silesia (polish - Slask, german - Schlesien, czech - Slezsko) became Polish, German mineralogists made chemical gravimetric analysis of the ankerites of this area:
Eisenhuth 1902 ( Walbrzych/Waldenburg)
MgO - 15.01%
FeO - 9.69%
CaO - 29.69%
CO2 - 44.84%
Hoehne 1944 ( Walbrzych/Waldenburg - Graf Hochberg Grube)
MgO - 11.58%
FeO - 12.20%
MnO - 2.80%
CaO - 28.60%
CO2 - 44.55%
Hoehne 1944 ( Walbrzych/Waldenburg)
MgO - 12.80%
FeO - 12.42%
MnO - 1.00%
CaO - 28.50%
CO2 - 44.60%
Hoehne 1944 (Wolibórz/Volpersdorf - Nowa Ruda/Neurode area)
MgO - 12.60%
FeO - 8.63%
MnO - 0.90%
CaO - 29.92%
CO2 - 43.10%
As attachment a map accroding to M.Ptak
13th Feb 2018 12:34 UTCFranz Bernhard Expert
thank you very much for the data, but unfortunately none of these minerals is ankerite by modern definition.
Franz Bernhard
13th Feb 2018 14:06 UTCKrzysztof Andrzejewski
.................................................................................................................................
the sample No2 ( Graf Hochberg Grube) FeO - 12.20% MgO - 11.58% too?? So now I'm lost totally....
13th Feb 2018 14:34 UTCFranz Bernhard Expert
I supposed that your analyses are wt%. If so - yes.
But no need to be lost, thats usuall case, that the old ankerites are Fe-rich dolomites according to the actual mineralogical nomenclature.
Franz Bernhard
13th Feb 2018 15:15 UTCAlfredo Petrov Manager
13th Feb 2018 17:00 UTCJeff Weissman Expert
13th Feb 2018 17:09 UTCJeff Weissman Expert
Updated entry for "ankerite" from Wheatley Mines - https://www.mindat.org/loc-4075.html
Updated entry for "ankerite" from Phoenixville Tunnel - https://www.mindat.org/loc-51015.html
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Copyright © mindat.org and the Hudson Institute of Mineralogy 1993-2024, except where stated. Most political location boundaries are © OpenStreetMap contributors. Mindat.org relies on the contributions of thousands of members and supporters. Founded in 2000 by Jolyon Ralph.
Privacy Policy - Terms & Conditions - Contact Us / DMCA issues - Report a bug/vulnerability Current server date and time: April 24, 2024 13:56:52