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I hate when that happens: Anthophyllite? Buckwheat Dolomite

Posted by Modris Baum  
I hate when that happens: Anthophyllite? Buckwheat Dolomite
May 10, 2012 01:29AM
    
This is a talk page topic. Click the thread header photo to see more info.

Anthophyllite is one of several minerals that has come and gone from the Buckwheat Dolomite (Franklin NJ) list. It's still a valid mineral - but not at Franklin.

Does anyone know what has happened with this?

Thanks - Modris



Edited 1 time(s). Last edit at 05/10/2012 02:34AM by Modris Baum.
Re: I hate when that happens: Anthophyllite? Buckwheat Dolomite
May 11, 2012 08:22AM
    
Modris,

I cannot help in answering what happened at the locality entry, but I am curious on the environment in which the "anthophyllite?" of your photo has formed. Can you share any information on associated minerals testing etc.?

The reasoin I am asking is that anthophyllite is formed ( as a general rule of thumb, not without exceptions) in relatively high PT environments associated with other Mg minerals such as talc, phlogopite, magnesite, chlorite etc, with a high Mg/Ca ratio. It appears from your photo that the "anthophyllite?" has formed with dolomite as a late hydrothermal mineral. If so, it would be an unusual association for anthophyllite, and therefore very interesting.

smiling smiley

Olav
Re: I hate when that happens: Anthophyllite? Buckwheat Dolomite
May 11, 2012 11:44AM
Yes, this is deffinately a strange occurance, I'v never heard of Anthophyllite forming in or on or with dolomite before, as Olav said, anthophyllite is usually a mineral from high PT environments!
avatar Re: I hate when that happens: Anthophyllite? Buckwheat Dolomite
May 11, 2012 01:57PM
Normally, if a mineral has previously been reported from a site, but is now known NOT to occur there, it should remain in the mineral list but marked as "erroneously reported" along with a reference to the discreditation.

Minerals should not just be deleted from lists because you "know it's not found there".
Re: I hate when that happens: Anthophyllite? Buckwheat Dolomite
May 11, 2012 05:08PM
    
Olav & Jolyon,

The occurrence is in the so-called "Buckwheat Dolomite". According to Palache (1935) and Dunn (1995) it occurred as a "veinlike mass of gray dolomite" in the west wall of the Buckwheat Open Cut in the Franklin Mine. ... [the] varied minerals, however, have no evident relation to the Zn-Mn-Fe character of the orebodies." (See Buckwheat Pit for the references as well as a species list - which however includes minerals from the orebody as well as from the dolomite.)

Peters et al (1983) published a list of mineral found in this environment In the Mineralogical Record but I don't have a copy of this article and I don't know if "anthophyllite" was on this list. However the Feb 1961 issue of The Picking Table (Vol 2, #1) states that "the list of Franklin-Ogdensburg mineral species validated by Professor Frondel has been brough up to date. Several additions have been made: allmandite, anthophyllite ..."

Frondel's book The Mineralogy of Franklin and Sterling Hill, Wiley, 1972) does not list anthophjyllite for the Buckwheat Dolomite. Instead, anthophyllite is attributed to "slickensided surfaces composed of tremolite, often asbestiform, or less commonly of antigorite, chryotile or anthophyllite admixed with calcite, or finely divided zincite or franklinite."

Kushner (A Guide to Mineral Collecting at Franklin and Sterling Hill, New Jersey, Kushner Books, 1974), states that anthophyllite "Sometimes looks like Asbestos; found at Sterling Hill and Franklin. First identified by [John] Baum in 1960." Associated with "calcozincite".

Nevertheless it seems that collectors attributed "anthophyllite" to the Buckwheat Dolomite as well - at least ca 1970.

Frondel's list of Buckwheat Dolomite species (1972) was: albite, anatase, anglesite, apatite, barite, brookite, calcite, celestite, dolomite, franklinite, goethite, graphite, greenockite, gypsum, hematite, hemimorphite, heulandite, ilmenite, manganite, millerite, pyrite, pyrrhotite, quartz, rutile, siderite, sphalerite, stilpnomelane, talc, zircon.

I think that any list made today would differ substantially - with additions, subtractions and re-definitions. But Frondel's list probably gives a good idea of the environment. (Note however, that there are several "scaly" minerals in the Dolomite that don't seem to match anything on the Mindat Buckwheat Pit list.)

Warren Cummings proposed a genetic model in The Picking Table (Vol 29, #2, 1988), but only mentions a few specific minerals and that "as many as 41 minerals have been listed ..."

My take is that anthophyllite should probably have never been attributed to the Buckwheat Dolomite in the first place. But I don't really know the history behind this particular attribution. As for anthophyllite at Franklin in general, I can find no explanation of why it has disappeared from the list(s).

Which leaves me with my original question: "What is it?" smiling smiley

Modris



Edited 1 time(s). Last edit at 05/11/2012 05:11PM by Modris Baum.
Re: I hate when that happens: Anthophyllite? Buckwheat Dolomite
May 12, 2012 06:53AM
    
Modris,

Thank you for your detailed account on the "Buckwheat dolomite". To me, Frondel's description of anthophyllite as occuring with tremolite and serpentine in slickensides seems in line with how the mineral occurs other places. I think that a "erroneously reported" status might be considered for anthophyllite at the Buckwheat Pit, although "Mark Germine and John H. Puffer(1981): Distribution of asbestos in the bedrock of the northern New Jersey area, Environmental Geology Volume 3, Number 6 (1981), 337-351 might shed a light on the occurence of anthophyllite in Franklin. The abstract is available here.

I am afraid that I will not be of much help with your "what is it?" question though.

Olav
avatar Re: I hate when that happens: Anthophyllite? Buckwheat Dolomite
May 12, 2012 01:13PM
I agree anthophyllite is pretty doubtful in this assemblage, it may be tremolite?

Regards,
Ralph
Re: I hate when that happens: Anthophyllite? Buckwheat Dolomite
May 12, 2012 01:25PM
    
Olav & Ralph,

Thanks for your responses.

How about actinolite (as in "byssolite")? At least it is on the current Buckwheat Pit list.

Modris
Re: I hate when that happens: Anthophyllite? Buckwheat Dolomite
May 22, 2012 07:25PM
    
Modris,

If what you have is an amphibole, calling it byssolite in the meaning "fibrous or hair-like amphibole formed under relative moderate P/T conditions and of tremolite or actinolite composition" would probably be as close as you will get on this one.

I'm not sure if there are any other agicular, white minerals from the Buckwheat Dolomite that it may be though.

Olav
Re: I hate when that happens: Anthophyllite? Buckwheat Dolomite
May 22, 2012 08:28PM
    
Thanks Olav,

I'm probably going to leave it as undetermined. While actinolite is listed for this environment I don't know what it looks like here so I don't want to muddy the waters.

It's not a big deal for me. I was just curious if anyone knew what happened to the supposed "anthophyllite". Seems like it went as quietly as it came,

Modris



Edited 1 time(s). Last edit at 05/22/2012 10:36PM by Modris Baum.
Re: I hate when that happens: Anthophyllite? Buckwheat Dolomite
May 23, 2012 12:52AM
Modris,

I don't think I have ever seen a verified anthophyllite from the Buckwheat Dolomite and may have been wishful hallucination of prior collectors. As you may know the amphibole, magnesioriebeckite does occur in the dolomite and there are many examples of this in private and public collections, e.g., Franklin Mineral Museum. The actinolite from the dolomite is normally a compact fibrous mass. I want to add that the actinolite was not, to my knowledge, analyzed.

Your white acicular crystals may well be a carbonate like aragonite or sulfate like barite or celestine.

Peter
Re: I hate when that happens: Anthophyllite? Buckwheat Dolomite
May 23, 2012 01:09AM
    
Hi Peter,

Thanks for the info. It's what I was fishing for. I'll try so HCl to see if the stuff vanishes. (Although - truth to tell - I was more intrigued by the "anthophyllite" ID than by the specimen itself.)

Modris

PS Yes - I have seen the magnesioriebeckite. In fact I found some many years ago. Quite different looking stuff.
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