Editing Gemology (section)

==Background==
It is often difficult to obtain an expert judgement from a neutral laboratory. Analysis and estimation in the gemstone trade usually have to take place on site. Professional gemologists and gemstone buyers use mobile laboratories, which pool all necessary instruments in a travel case. Such so-called travel labs even have their own current supply, which makes them independent from infrastructure. They are also suitable for gemological expeditions.

Gemstones are basically categorized based on their [[crystal structure]], [[specific gravity]], [[refractive index]], and other optical properties, such as [[pleochroism]]. The physical property of "hardness" is defined by the irregular [[Mohs scale of mineral hardness]].

Gemologists study these factors while valuing or appraising cut and polished gemstones. Gemological microscopic study of the internal structure is used to determine whether a gem is synthetic or natural by revealing natural [[fluid inclusions]] or partially melted [[Exogeny|exogenous]] crystals that are evidence of heat treatment to enhance color.

The spectroscopic analysis of cut gemstones also allows a gemologist to understand the atomic structure and identify its origin, which is a major factor in valuing a gemstone. For example, a [[ruby]] from Myanmar (Burma) will have definite internal and optical activity variance from a Thai ruby.

When the gemstones are in a rough state, the gemologist studies the external structure; the host rock and mineral association; and natural and polished color. Initially, the stone is identified by its color, refractive index, optical character, specific gravity, and examination of internal characteristics under magnification.
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