Gem Info (Gem Testing)
Commonly Encountered Gemstones
A mineral is a naturally occurring, inorganic, homogeneous substance with a definite chemical composition and a regular three dimensional arrangement of atoms. A rock is an aggregate of minerals. From time immemorial several minerals and rocks have been used as gemstones. Nowadays not only minerals and rocks, any material, say metallic, amorphous, synthetic, organic or inorganic, that has substantial beauty, rarity and durability and can be fashioned into a desirable and attractive form is being used as a gem.
The table given below shows the gem varieties of some of the minerals/rocks commonly used as gemstones. The photos of the gemstones in the table below have been captured in the Gem Testing Lab of the Department.
An organic gem is one that was made by living things, present or past. Examples include pearl, coral, jet, ivory, shell, amber, ammolite etc. Such gems consist of the molecules formed by the organism, although these molecules may have been altered somewhat due to compression or other geological or chemical forces.
Synthetics and Simulants
Several of these gemstones are synthesized for commercial purposes. Synthetic gemstones correspond to their naturally occurring counterparts in crystal structure, physical, chemical and optical properties. Usually natural stones are distinguished from synthetic stones with the help of inclusions present.
Simulants are imitation gems that look like the natural or synthetic gems they imitate, but do not have the physical, chemical and optical properties of the gems they mimic. Two common gem simulants are glass and plastic.
Several treatments are done on gemstones to improve their colour, clarity and durability, thereby enhancing the general appearance and beauty of the stones. The common treatments done are: