You may be well aware that there are synthetic sapphires in the gemstone market. Getting what seems to be the best deal ever, may well be a 'too good to be true'. Here are some tips you can follow before deciding to buy.
See it directly. There is a lot of difference when looking at gemstone online versus directly using your own eyes. This is because when we try to capture the color and beauty of green sapphire, our camera lens may capture it differently.
Ask for gem inspection under natural light. By far, natural sunlight is the best light you can get when seeing gemstone. After all, the sunlight is coming from the same sun you are used to whether you are in Thailand or in Europe (or anywhere else)
Certificate. This piece of paper may contain details of your green sapphire. It is a very useful information, and make sure you keep it well.