A gemstone called a gem,fine gem,jewel,precious stone,or semi precious stone is a piece of mineral crystal which is in cut and polished form, is used to make jewelry or other adornments. However the certain rocks such as lapis lazuli and opal and occasionally organic material that are not minerals such as amber and pearl are used for jewelry and are often considered to be gemstones as well most gemstones are hard, but some soft minerals are used in jewelry because of their luster or physical properties that have aesthetic value.
Apart from jewelry from earliest antiquity engraved gems and hardstone carvings such as cups were major luxury art forms in modern times gemstones are identified by a gemologist who describe gems and their characteristics using technical terminology specific to the field of gemology.
Gemstone are classified into different groups, species and varieties for example, ruby is the red variety of species corundum, while any other color of corundum is considered as sapphire.Other example are the emerald, aquamarine, red beryl and morganite which are the varieties of the minerals species beryl.
Gems are characterized in the terms of refractive index, dispersion, specific gravity, hardness and lustre.
There are number of laboratories which grade and provide reports on gemstones.
- GTL (Gem Testing Laboratory). Time period is one day.
- GIA (Gemological Institute of America), The main provider of the diamond grading reports. Time period is 3 months.
- IGITL (International Gemological Institute and testing laboratory),for grading and evaluation of diamonds, jewelry, colored stones. Time period is sameday.
- AGL (American Gemological laboratory). Time period is 3 months.
- GRS (Gemological research station). Time period is sameday.
- AGR (Advance Gem Research ). Time period sameday
- Gemtrue Time period is sameday.