[Rockhounds] Scapolite

[Axel Emmermann]

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 paper 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