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Eudialyte, Aegirine

Eudialyte : Na15Ca6(Fe2+,Mn2+)3Zr3[Si25O73](O,OH,H2O)3(OH,Cl)2, Aegirine : NaFe3+Si2O6

Photo Copyright © Rob Lavinsky & irocks.com  - This image is copyrighted. Unauthorized reproduction prohibited.
Dimensions: 6.1 cm x 5.3 cm x 4.3 cm

6.1 x 5.3 x 4.3 cm. A rich and showy specimen of sharp and lustrous, chocolate-colored eudialyte crystals to 1.4 cm associated with black aegirine as a nice accent, from very close to the Type Locality in Greenland. There is contacting, but this is a highly representative specimen of the two species and locality. Originally labeled as zircon altering to eudialyte, this is unlikely. I've been told that there are "numerous references in papers of mineralogy, petrology and geochemistry of Zircon replacing Eudialyte, but not the other way around. There is known one report of Eudialyte formed hydrothermally with indications of Zr being mobilized from preformed Zircon (in the Pilanesberg complex of South Africa eudialyte is interpreted to be hydrothermal formed from an orthomagmatic Na-Nb-REE-Cl-F-solution that exsolved from an agpaitic syenitic magma. In this system the Zr was probably remobilized from an originally formed magmatic zircon. But under such conditions any direct replacement in the form of pseudomorphs would be very unlikely from the petrological description.) This is not the case here. Ex. George Ellng Collection.

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Photo added: 7th Dec 2007

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