WHAT IS CORUNDUM?
Corundum is an extremely hard crystalline rock (9 on the Mohs scale of hardness) made from aluminium oxide and is used industrially as an abrasive.
Rubies are gem quality Corundum with all the red shades from pinkish to purplish or brownish red depending on the chromium content within the stone.
The most sought after rubies are described as being “pigeon blood” red and have a dark deep red hue and come from Myanmar.
Sapphires are also gem quality Corundum and range from colourless through the colour spectrum to almost black. The most sought after are clear deep blue sapphires from Kashmir.
Pink sapphires which look similar to very pale rubies range from very pale pink through to purplish pink due to iron and titanium within the stone and so can be described scientifically as sapphires as they do not contain so much chromium.
Green and yellow sapphire are also widely used in jewellery manufacture.