Always make a careful, naked-eye observation of the gemstone you intend to buy. Observe the gem in all directions under different lighting conditions (natural light, incandescent, fluorescent, halogen). This first careful observation is the key to establishing the identity, characteristics and quality of the material under analysis.
Hold the stone in your fingers and feel it. Don't use tweezers or magnifying lenses at this stage.
Pay close attention to the color of the gemstone. It is normally this first color impression that will indicate the origin of the stone, whetherit is natural, and what country it is from or whether synthetics or imitations should be suspected.
Don't forget that color is the most important factor in the price evaluation of colored gemstones and the most difficult to determine. If you are not proficient in the color subtleties of the stone you are observing, seek the assistance of a qualified gem dealer.
Carefully study the surface of the gemstone by tilting it and using oblique lighting techniques to view the surface. If cracks and fissures are detected with the naked eye, it is a sign of a highly -treated stone that could be damaged easily. Make sure the gemstone surface is free of grease, dust or anything that might interfere with your observation.
Carefully observe the brilliance of the stone and the faceting style. These elements will be considered in the identification and price evaluation process.
Once this initial observation stage is completed and if you have not observed damages that could endanger the stone, proceed to handle the stone with tweezers and a 10X loop.
Study the stones' transparency and clarity, the second most important aspect in price evaluation.
Look closely at the features that will confirm the right identity of the gemstone. Pay close attention to the inclusions. This can yield a fair assessment of the mine origin. And, this can affect overall brilliance and durability of the material.
Continue by studying the surface of the stone, make sure you are not looking perpendicular to the surface, but in an oblique fashion. This technique will allow you to observe the treated areas of the stone starting from the surface where the treating agent was introduced. Alternate between dark and light backfields. This will aid your observation of the internal features and fractures. Try to determine the origin of the enhancing material that will affect the overall presence and durability of the stone in the future. When in doubt, seek the assistance of a qualified gem testing laboratory.
Observe the overall cutting and polishing of the surfaces. This is the third most important factor in the price assessment of a gemstone. It will affect the brilliance of the gemstone.
Shape and overall balance and harmony of form are important factors in the marketability of gemstones. Keep this in mind.
Don't forget the maxim, "It's too good to be true," when presented with a gemstone at a below market price. Be aware, the material is either something different from what it appears to be under naked eye observation or its provenance is doubtful. Keep away from both situations.
Don't forget the most important factor in buying gemstones is to do it whenever possible through well established, reputable dealers or jewelry stores.
When buying a gemstone, if you do not have experience, request a Gemological Certificate of Identification, issued by a qualified third party not related in any manner to the seller.
The buying tips given here apply best to loose stones. Gemstones set in jewelry are generally more complex to identify and evaluate, especially if set low on the mountings.
There are gemologists and qualified laboratories in most major cities in the world. For a partial listing, please refer to the section Gem Labs For further referrals and gemstone information, please refer to the section on Trade Organizations, Education.