Opal var: Opal-AN (formerly ''Hyalite Opal'') (rare PURPLE color)

Item Description

An interesting an unusual example of Opal from the Erongo Mountains of Namibia. This material for years was labeled as "Hyalite", but recently has been re-classified as Opal-AN, a variety of Opal which forms as a series of dissimilarly-sized nanospheres of silica that measure less than 5 nm in diameter, according to entry on mindat.org. This specimen is filled with dozens of aggregates of gemmy, colorless Opal-AN, covering the display side of this small cabinet sized specimen, but the MOST interesting aspect can really only be seen under magnification, because when you look closely, you'll see small zones of PURPLE inside of the Opal, which is an incredibly rare hue to find in this material. As first I thought that this might be due to minor Fluorite inclusions within the Opal, but when we looked at it under the microscope (and with our close-up lens on the camera), it appears that the color is truly not caused by another mineral, as there are simply "bands" or zones of color, and not crystals included within the Opal. It's the ONLY piece I can remember seeing that shows this unusual hue. Additionally, one of the characteristics of this material is it often is highly fluorescent, and this piece shows a glowing electric green color under SW UV light. A really cool and desirable specimen of this beautiful material that is pegmatitic in origin, not volcanic, like most Opal-AN specimens.