Gemological report terminology & nomenclature

Weight                           

The force that a gravitational field (for example the terrestrial one) exerts on a body having mass. In the International System, it is expressed in kilograms of which the gram is the thousandth part, while in gemology the metric carat (ct) equivalent to 0.200 g is used as the unit of measurement. It is commercially expressed to the second decimal place.

Cut style        

Preordered design composed of a number of flat surfaces (facets in brilliant or step cuts) and/or curves (a.e. cabochon) resulting from cutting operations.

Shape             

It is defined by the external appearance of the figure and identified according to the shape of the outline of the gem

Dimensions                

A group of measures of spatial extent, specifically length, width and height of an object, expressed in millimeters to the second decimal place.

Color             

The perception of the appearance of objects that may be described in terms of hue, lightness (value), and saturation (chroma). Color of Gems is graded by comparison with reference based on the Munsell Color Standard.

Transparency                       

The property of a body by which it transmits light so that objects can be clearly seen through it, even through a considerable thickness. The grade of transparency can be: transparent, semitransparent, translucent, semitranslucent and opaque.

Fluorescence             

The emission of visible light caused by exposure to invisible radiation (such as Ultraviolet Wavelengths (UV), X Rays, Cathode Rays). It ceases when the incident radiation stops. UV Fluorescence is graded by comparison with reference standards.

Enhancement            

Artificial process altering the appearance and properties of gemological material to improve its appearance. When present, Enhancements are described by using the terminology established in the Laboratory Manual Harmonization Committee (LMHC) Information Sheets (https://www.lmhc-gemmology.org/gemstones/)

Geographic origin    

Opinion of the Gemology Resources laboratory staff about the specific geographic origin of the gemological material. It is based on the comparison of a number of features with references of known provenance.

Species           

Classification of minerals based on their chemical composition, crystal structure and physical and optical properties.

Variety          

Subclass of species depending on color, color distribution, kind of optical phenomenaor other distinguishing appearance characteristics.