- Natural Gem:- A gem material which is completely the product of nature and which is unaltered by humans except for ordinary cutting and polishing.
- Treated Gem:- Any gem material which has been treated to either improve clarity or to enhance its colour by using various treatments beyond ordinary cutting and polishing.
- Synthetic Gem:- Synthetic gems possess same chemical compositions, structure, properties and appearance as their natural counterpart or seed crystal. They are not made by nature but created by humans.
- Manmade Gem:- Similar as synthetic gem but has no natural counterpart or seed crystal.
- Assembled Gem:- Any gem material natural or otherwise which is created by assembling two or more pieces of similar or different materials along different junctions.
- Imitation Gem:- Any gem material natural or otherwise which has the same look as the gem it imitates.