Larion Kantor
Gemstones classification
Larion Kantor
Gemstones classification
There are many terms in gemmology and jewelry that are easy to get mixed up. In this article we will sort through the terms of gemstones classification. 

Gemstones are classified by the following principles:
1. Origin
By origin gemstones are classified as natural, created as a result of natural processes, and synthetic, made by human hand.

Synthetic gemstones - crystals made by humans.

They can be:
  • having a natural counterpart (adamant, corundum)
  • not having a natural counterpart (cubic zirconia)

If a synthetic gemstone fully duplicates physical and chemical characteristics of his natural counterpart, it receives the same name as the natural one but with an obligatory statement - “synthetic” or “lab-grown”
If the synthetic gemstone doesn’t have a natural counterpart, then it gets a separate name.

Nowadays, adamants, alexandrites, amethysts, emeralds, rubies, sapphire and other gemstones can be grown in a laboratory.

You shouldn’t confuse synthetic gemstones and imitations.

Imitations are jewelry additions that duplicate only the appearance of natural minerals. They can have a number of similar physical characteristics but a totally different chemical pattern. Imitations can be of both natural and artificial origin. For example, cubic zirconia can become a diamond imitation and natural colored beryl can be an imitation of an emerald.

Natural gemstones can be divided into organic and inorganic ones.

A few of the organic ones are amber, pearl and coral. These materials were born out of living organisms.

Inorganic gemstones are minerals with a crystal lattice that meet the standards of beauty, durability and rarity.

  • Gemstone beauty depends on it’s clarity, color, sparkle, purity and other optical characteristics.
  • Rarity depends on the amount of mined gemstones and it’s abundance in nature.
  • Durability depends on the material’s hardness which is affected by internal defects and inclusions.
Combination of these measurements defines the value and price of each sample. 
Inorganic gemstones are usually divided into adamants and colored gemstones. First of all, it’s caused by the adamants' hardness. Jewelers use a special tool to work with it. Second of all, the market situation differs. Today diamonds are more liquid, fluctuations in their value can be easily tracked on the Rapaport price list, which makes them a more reliable investment. 
Treatment method
The majority of natural gemstones have a number of imperfections that taint the beauty and impact the durability. Those might be cracks, different inclusions, color dissimilarity. Gemstones can go through the process of treatment in order to improve the characteristics (color, clarity, purity) and prolong it’s life. 

Gemstones that were not exposed to anything else besides cutting and polishing are considered untreated.

Different treatment methods are applied both before and after cutting. Some of them are easy to detect, others are hard to determine even in large laboratory evaluations. 

Manufacturers and dealers don’t always inform about the fact of  treatment. 

According to The World Jewellery Confederation (CIBJO), treatment methods are divided into General (commonly accepted methods that don’t require obligatory customer acknowledgment) and Specific (methods that are required to be indicated). The second category includes:
  • treatment result might be unstable (might change during routine wear set in a jewelry piece or cleaning), 
  • treated piece requires special care,
  • the fact of treatment affects the price a lot 

For instance, color treated diamonds are a lot cheaper than untreated ones with the same characteristics. 

Most common treatment methods are heating, impregnation, wax coating, fracture or cavity filling, HPHT treatment, irradiation and laser inclusions removal.

The use of certain treatment methods directly affects the cost, durability and investment value of the gemstone. 
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