[Rockhounds] Scapolite again

Wed Oct 1 11:02:34 PDT 2008

Hi to Axel & the others (in case anybody still does care more about "scapolite"),

At the risk of repeating info that may already have been mentioned here (without reading back over all the past posts on this topic),

I'm still thinking about scapolite off and on, so, Axel et al., were you aware of the most recent paper about scapolite that appeared in American Mineralogist, Aug-Sep 2008; the abstract is posted on the MSA website at,

http://www.minsocam.org/MSA/ammin/toc/Abstracts/2008_Abstracts/AS08_Abstracts/Antao_p1470_08.pdf

Unusual Al-Si ordering in calcic scapolite, Me79.6, with increasing temperature, by Sytle M. Antao and Ishmael Hassan

Reading it reminded me, among other things, that the sulfate end-member of the scapolite group HAS been officially described as a separate mineral species, silvialite.? That name was used much earlier (1914, according to Mindat.org) for the hypothetical sulfate scapolite end-member, but it was officially approved in 1998, and published in 1999, for the type locality being in Queensland, Australia.? Just two pictures of silvialite are posted on the Mindat gallery, both from 
Loitsch Quarry, Weida, Gera, Thuringia, Germany

That's all for now!

Pete

-----Original Message-----
From: pmodreski at aol.com
To: rockhounds at lists.drizzle.com
Sent: Fri, 26 Sep 2008 9:50 am
Subject: Re: [Rockhounds] Scapolite

"It's probably the same with series like calcite - rhodochrosite."

Not quite the same situation, Axel, because with the carbonates, relatively pure 
calcite is by far the most common, then with varying small amounts of manganese 
making the manganoan calcite ("manganocalcite") varieties.? Then it's also 
complicated by the existence of the intermediate compound analogous to dolomite, 
namely kutnohorite, CaMn(CO3)2 .? I believe that the special issue of Min. 
Record dedicated to the Sweet Home mine, July-August 1998, in the article by 
Karen Wenrich, included a diagram or a table showing compositions of Sweet Home 
rhodochrosite analyzed by microprobe, showing how the compositions are 
distributed as regards Ca vs. Mn content; and that the gemmy red rhodochrosites 
were purest in Mn, and the paler, cloudy-pink ones contained more Ca.? I don't 
have the issue at hand right now or I'd look this up and refresh myself as to 
exactly what it shows.

Pete

-----Original Message-----
From: Axel Emmermann <axel.emmermann at pandora.be>
To: 'Rockhounds at drizzle.com: A mailing list for rock and gem collectors' 
<rockhounds at lists.drizzle.com>
Sent: Fri, 26 Sep 2008 3:24 am
Subject: RE: [Rockhounds] Scapolite

Hi Pete,

Thank you for sending the list.
I guess the scapolite story is no different from most continuous series. If
you look at the results:

0-20% meionite: 2 samples 
20-40% meionite: 5 samples 
40-60% meionite: 7 samples 
60-80% meionite: 5 samples 
80-100% meionite: 1 sample 

Now that is a classical Gaussian bell curve if ever I saw one. ;-)))

It's probably the same with series like calcite - rhodochrosite.

Cheers
Axel

> -----Oorspronkelijk bericht-----
> Van: rockhounds-bounces at lists.drizzle.com
[mailto:rockhounds-bounces at lists.drizzle.com]
> Namens pmodreski at aol.com
> Verzonden: donderdag 25 september 2008 22:34
> Aan: rockhounds at lists.drizzle.com
> Onderwerp: Re: [Rockhounds] Scapolite
> 
> (OK, anybody tired of hearing about scapolite, just delete this!)
> 
> A little more data, for Axel & all,
> 

> (1) I looked through my files and found a good article, by Teertstra &
Sherriff, 1996, Am.
> Min. v. 81, 169-180 (it should be online too, via the MSA website), which
gives complete
> chemical analyses, and other (XRD, etc.) data, for some 20 scapolite
samples from around the
> world.? For my own interest I typed out a list of the 20 localities and
their composition in
> terms of % of the meionite (calcium) endmember--if anyone would like to
see this, please just
> write to me & I'll email it back to you.? But here is a quick summary of
what it shows:
> 
> 0-20% meionite: 2 samples (Pamirs, Russia, light violet gem crystal, and
Gooderham, Ontairo,
> opaque blue-gray)
> 20-40% meionite: 5 samples (Quebec, Ontario, Tanzania, Brazil)
> 40-60% meionite: 7 samples (Quebec, Ontario, New York, Madagascar,
Tanzania)
> 60-80% meionite: 5 samples (Quebec, Massachusetts, Russia (Slyudyanka)
> 80-100% meionite: 1 sample (Monte Somma, Italy; 96.5% meionite)
> 
> This article also mentioned that it used, as a standard for microprobe
analysis, a "gem quality
> meionite from Brazil, U.S. National Museum No. R6600-1", but it doesn't
give the exact
> composition of that specimen.
> 
> (2) I see that there was also a pa
per published, "On the composition of
gem scapolites", by
> Pete J. Dunn et al., 1978, Journal of Gemmology, v. 16, pp. 4-10.? I don't
have a copy of this
> paper now, but I'm requesting one via our library.
> 
> (3) The mention above of the USNM meionite gave me the idea of checking
the U.S. National
> Museum of Natural History's (Smithsonian Institute) catalog, which is
searchable online--it
> is at,
> http://nhb-acsmith1.si.edu/emuwebmsweb/pages/nmnh/ms/Query.php
> The result is interesting--I searched according to what mineral name
specimens are
> catalogued under, which of course is subject to the same caveats expressed
here for Mindat
> entries--yes, I agree, one doesn't know how accurate the "meionite vs.
marialite" entries for
> any of the specimens are, though one might hope that the Smithsonian
catalog 
information is
> more authoritative than most.? Here's what the catalog shows:
> 
> "Scapolite" - 621 entries
> 
> "Marialite" - 35 entries (including 8 from U.S., 6 Canada, 6 Tanzania, 3
Madagascar, 1 Brazil,
> 1 Mozambique)
> 
> "Meionite" - 67 entries (including 25 "Vesuvio", 8 Brazil, 7 U.S., 6
Canada, 2 Madagascar, 1
> Tanzania, 1 Kenya, 1 Burma)
> 
> "Wernerite" - 12 entries
> 
> "Mizzonite" - 18 entries
> 
> Of course, most of the Smithsonian specimens I'm sure have not been
analyzed,?but just
> catalogued under the mineral name by which they were received; hence, the
large number of
> "just plain scapolite" entries.
> 
> Pete

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