Concept in Definition ABC

A gem is a precious stone, that is, a mineral that when cut and polished can be used in the manufacturing jewelry or any other type of decorative ornament. Among the best known gems we can highlight the following: opal, sapphire, topaz, azurite, agate, diamond or turquoise.

Certain gems are of organic origin, such as natural pearls or coral. They all have some common characteristics: a certain beauty, a striking color, a degree of transparency and an intensity in its brilliance. The discipline scientist who studies gemstones is gemology.

Gemology as a science

This discipline is relatively recent, since it is the 20th century when the first institutions academics in this area of ​​knowledge. Gemology is integrated into a more general area, mineralogy and this is, in turn, a branch of geology.

Although it is based on theoretical principles, in practice it is oriented to the world business, specifically to the sector of ornamentation or jewelry.

Gemologists use their own instruments, which are very different from those used by geologists. In this sense, utensils are used that cannot damage or deteriorate precious stones.

Gemologists look at the different physical and optical properties of gemstones. Thus, each stone or gem has its specific weight, its color, its refractive index, its type of spectrum or its level of hardness.

The hardness of gems

To the margin From the beauty, color or brilliance of gemstones, gemologists study the hardness of gemstones. This property does not simply refer to the possibility of breaking these pieces with greater or lesser difficulty, but refers to the endurance to scratching. To measure this property the so-called scale of Mohs.

This scale objectively describes the hardness of a gem. For this, a table from 1 to 10 is established, where the number 1 indicates a minimum degree of hardness and 10 a maximum degree.

Each gemstone can be compared to another using the following table of equivalences:

level 1 is represented by talc, 2 corresponds to gypsum, 3 to calcite, 4 to fluorite, 5 to apatite, 6 with orthoclase, 7 with quartz, 8 with topaz, 9 with corundum and, finally, 10 with diamond.

Talc has a lower hardness because it can be scratched with a fingernail, apatite has a level 5 and is scratches with difficulty with a piece of steel and the diamond is only scratched with tools specialized.

Photos: Fotolia - Nikki Zalewski / alesikka