This classic ring features a cushion shaped 10.33 carat spinel in a diamond surround. It comes up for auction @sothebys in Paris on April 30.
Pure spinel is colourless; it is trace elements (e.g. cobalt or iron) that cause its many different colours, such as red (the most valuable variety), but also in violet hues, light to deep blue, orange, yellow, brown and black. - 50 minutes ago