Q: Is it possible to identify synthetic diamonds from Natural ones? How?
In the most commonly selling grades such as VS, SI and below, you can very much distinguish the synthetic from a natural diamond. Look in the loupe for the 'synthetic' characterstics such as the carbon deposits and hour glass zoning.
HTHP (High Temperature High Pressure synthetic diamonds) are easier to identify because of the hourglass and the 'hexagon' sort of bands but CVDs (Carbon Vapor Deposited) are much more tricky because their inclusions are very similar natural inclusions.
So the better quality ones such as VVS and over are really really tough to make out especially if they are CVD Diamonds. You would definitely require advanced instruments for those.
To figure out natural vs synthetic diamonds, practise a LOT. Get a bunch of synthetics of various kinds and grades and a bunch of real ones. Look very very carefully to compare the inclusions, their color, reaction in the various advanced gemological instruments. You will be able to eventually make out differences.
While assessing the stones, if you come across obvious natural or obvious synthetic inclusions, you can move on to the next stone. After that point, go on to the advanced instruments. Beyond that you would need to seek external help from bodies such as GIA or EGL etc.