September's birthstone colour is the vibrant sapphire. Sapphire is a relation to our previous birthstone blog post - July's ruby. This is because both stones are forms of the mineral corundum. Sapphires are typically blue stones, with the colour caused by small amounts of titanium and iron in the crystal structure.
The shade of stone ranges from pale blue to deep indigo, the most valued of which is somewhere in between - a medium-deep cornflower blue. The biggest source of sapphires in the world is known to be Australia, alongside many valuable stones found in Kashmir, India. One of the most famous stones can be found on the Imperial State Crown, worn by Queen Victoria in 1838. This now lays amongst the British Crown Jewels in the Tower of London.