SAPPHIRES
The name “sapphire” can also apply to any corundum that is not ruby red, another variety of corundum.
Besides blue sapphire and ruby, the corundum family also includes so-called “fancy sapphire”. They come in violet, green, yellow, orange, pink, purple and intermediate hues. Some stones exhibit the phenomenon known as colour change, most often going from blue in daylight or fluorescent lighting to purple under incandescent light.
The blue sapphire can be a pure blue but ranges from greenish blue to violetish blue.
In its purest state, corundum is colourless but most corundum contains colour causing trace elements responsible for the gem colour. When the trace elements are iron and titanium, the corundum is blue sapphire; the more iron the corundum contains, the darker the blue.