Wednesday, March 23, 2011

We asked for the difference between calcite and alabaster. Greg Merkel, a research fellow at Corning Incorporated supplies some answers.

I can say that every Gold Aurene decorated green & white or red & white vase (and one nut dish or bon-bon) that I’ve had the opportunity to non-destructively chemically analyze by x-ray fluorescence has been on a Calcite base glass, which is not to say that there couldn’t be versions on Alabaster. As many of our readers are aware, Calcite displays “opalescence,” meaning that it (normally) imparts a slight orange hue to transmitted light (when it has sufficient translucency). Note that if the object has a Gold Aurene lining or casing, any transmitted light will be orange or amber due to the silver particles in the Aurene, and won’t be a reliable test for opalescence. By contrast, Alabaster does not display opalescence. The difference in behavior is entirely due to the size of the light-scattering particles, which are smaller in Calcite. (The particles also happen to be of a different composition in Calcite versus Alabaster.)

That said, it’s certainly possible that there are exceptions out there, and we’d all love to see photos of them!

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