RUBIES
Ruby is the most valuable variety of the corundum mineral species; they can command the highest per-carat price of any coloured gemstone. This makes rubies one of the most important gems in the coloured stone market.
In its purest form, the mineral corundum is colourless. Trace elements that become part of the mineral’s crystal structure cause variations in its colour. Chromium is the trace element that produces the ruby’s red colour.
In its purest form, the mineral corundum is colourless. Trace elements that become part of the mineral’s crystal structure cause variations in its colour. Chromium is the trace element that causes ruby’s red, which ranges from an orangy red to a purplish red.
The strength of ruby’s red depends on how much chromium is present—the more chromium, the stronger the red colour. Chromium can also cause fluorescence, which adds to the intensity of the red colour.