We love gemstones here at Birmingham Stone Cutting. A diamond may be a girl’s best friend, but as far as we are concerned gemstones of any shape and colour fascinate us. Our Gemologist Lisa is a member of the The Gemmological Association of Great Britain, and has been identifying gems for over 20 years.
Gemstone identification is a specialised job. Here at Birmingham Stone Cutting we use a variety of techniques to establish the identity of gems depending on a variety of factors i.e. loose or in a setting.
For those of you who’d like to understand a little more about what we do and how we do it, we’ve included some interesting info below.
Gemstone Group/Family Classification
There are 16 mineral gemstone groups based on their chemical composition / crystal structure. The 16 groups are:
Refractive Index (RI) is one of the most important characteristcs of a gemstone.
Measuring the RI is one of the first steps we perform in identifying a gemstone, although some gemstones have very similar refractive indices, additional tests are sometimes required for a definitive identification.
Gems vary greatly in their density, this is why two gemstones may weigh the same but differ in size. All gemstones have a specific gravity and gemstones can be tested to determine their specific gravity or relative density.
Mohs Scale of Mineral Hardness
The hardness of a gem can be measured by its scratch resistance. This is done by testing the ability of a harder material to scratch a softer material. The Mohs scale was developed in 1812 by the German geologist and mineralogist Friedrich Mohs.
The hardest mineral in the Mohs scale of mineral hardness is Diamond and the softest is Talc. The number next to each mineral defines rank only, not relative hardness. For example, corundum (9) is twice as hard as topaz (8).
|1 Talc||6 Orthoclase (Feldspar)
|2 Gypsum||7 Quartz|
|3 Calcite||8 Topaz|
|4 Fluorite||9 Corundum|
|5 Apatite||10 Diamond|
Gemology is the study of natural and artificial gems and gemstones, click here if you’d like to learn more!