In most markets where valuable items are sold, counterfeits are produced due to the high profit margin. The sapphire market is no exception. The high price tag that comes with a sapphire depends on whether or not it is a synthetic (made in a lab), its clarity and its color. There are many means of making counterfeit sapphires look real. However, knowing a few characteristics of fake sapphires can save you from making a huge mistake as well as a lot of money.
Look for tiny bubbles in the sapphire. If there are bubbles present, the “sapphire” you are looking at is really glass.
Check for scratches. Sapphires are very hard and do not scratch easily, whereas glass is very easy to scratch.
Look at the sapphire’s cut. Real sapphires have sharp, complicated cuts whereas glass fakes have simple ones.
Examine the sapphire for imperfections, such as unevenness on the bottom and or stripes or lines of color that show through to the top. Most natural sapphires have these imperfections. Glass fakes look very pure, like a blue piece of glass.
Synthetic sapphires are not the same as fake sapphires. Synthetics are designed in a lab and have the same chemical makeup as sapphires found in caves.
References and ResourcesTheDiamond: Sapphire Guide
eBay Guides: How to Spot a Fake Blue Star Sapphire
Unique Fashion Jewelry With Diamonds and Gemstones: How to Identify Real and Fake Sapphire Jewelry?