Sapphires are bright blue gemstones used in both jewellery and as key components of industrial machines. While almost every sapphire you encounter will have gone through some sort of refinement or treatment process, it is important to know some of the warning signs that the stone you are looking at is a fake. Glass sapphires can be convincing fakes, so always double-check your stone before spending a large sum of money.
Examine the sapphire for tiny air bubbles using the jeweller's loupe. Bubbles are a natural part of glass formation and are a clear indicator of the stone being a fake.
Hold the stone up to a light source to check its clarity. All natural sapphires have minor imperfections and a stone with even, perfect clarity is almost certainly a fake.
Compare the colour of the sapphire to images of real, natural sapphires. Fake sapphires are often lighter and brighter than their real-life counterparts. Additionally, fake sapphires are usually one tone all over, while real sapphires express many shades of blue.
Check the surface of the stone for scratches. Sapphire is one of the hardest gemstones, while glass is very soft. A scratched-up surface is a telltale sign of glass composition.
Look for grooved facets on the stone. These are a common flaw found in lab-grown sapphires.
One of the best ways to spot a fake sapphire is using your common sense -- if a gemstone price seems too good to be true, it is probably not a real gemstone.