Loving the close up detailed shot of this late Victorian salamander brooch set with wonderfully vibrant, colourful opals, old cut diamonds and ruby eyes from Bonhams New York upcoming fine jewellery auction.
Alexandrite is very scarce: this is due to its chemical composition. It is basically a chrysoberyl, a mineral consisting of colourless or yellow transparent beryl (chrysos is Greek="golden"), and colour-changing alexandrite (also in cat’s eye varieties). It differs from other chrysoberyls in that it not only contains iron and titanium, but also chromium as a major impurity. And it is this very element which accounts for the spectacular colour change from green to red.