[Rockhounds] Scapolite

[pmodreski at aol.com]

Hello again, to Alex, Kreigh, Don, and anyone else who is still caring about reading more about our dear mineral friend, scapolite!

Two new items to add, one is that I obtained a copy of the 1978 paper by Pete J. Dunn (of Franklin-Sterling Hill, New Jersey, fame) + coauthors Nelen and Norberg,?on "The Composition of Gem Scapolites", from Journal of Gemmology (the Brit's spell it thus, with two m's), vol. 16, no. 1, pp. 4-10).? I'll just quote a bit from it here that is especially interesting, and to those who would like?(Alex, etc.), I can email a copy of the pdf file of the whole paper.? Pete reported that 

"Nineteen gemmy scapolites from the collections of the Smithsonian Institution were analyzed.? All the samples were of facetable quality except one from Canada.

"...the compositions of the gem material examined in the study vary from meionite72-marialite28 to meionite30-marialite 70.? All four specimens from Brazil are meionite, the calcium-rich end-member, and are quite similar in composition.? The examined Madagascar gems, however, are marialite, the sodium-rich end-member.

"Unlike the Brazilian meionites, the Madagascar marialites do vary widely in composition.? Burmese scapolites also have widely varying compositions and it is noteworthy that the most sodium-rich and most calcium-rich gems examined in this study do come from Burma.? The sample numbered G3783 is a superb 288 carat colourless gem and may be the largest cut scapolite in existence, in addition to being the most calcium-rich. 

"... The light yellow material from Tanzania, studied by Zwaan (1971), is marialite, as Zwaan noted in his excellent description of the material.

"The most unusual scapolite the authors have seen was brought to their attention by Mr. Herb Obodda, a noted American gem merchant.? This scapolite, reportedly from Tanzania, has a very strong yellow body colour and the piece examined is facetable.? The fluorescence of this material in ultraviolet radiation is remarkable for a gem mineral.? The fluorescent colours are a strong yellow in short wavelength ultraviolet and an extremely intense strong yellow in long wavelength ultraviolet.? There is no phosphorescence.? ... This yellow gem material is a meionite, unlike the other Tanzanian gems examined, and has a composition very close to the opaque Canadian material (#R13120), which has a similar if somewhat less intense fluorescence."

* * *


and a second scapolite item of interest, a picture and description of a purple, partially gemmy scapolite crystal from Afghanistan,?described as being meionite, is?shown in Thomas P. Moore's "What's New in the Mineral World?" column in the?latest?issue of the Mineralogical Record.??The column can be viewed online, it is posted at
http://www.minrec.org/whatsnew.asp
?
best wishes to all,
Pete Modreski
(and I still apologize for the way my wretched mismatch of email programs, puts all those extra darn question marks and stuff into my posts to this List!)





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