Gems Education

Precious and Semiprecious Gems

For centuries, people have used the terms precious and semiprecious to describe gemstones. You’ll still occasionally hear these terms today. However, this gem classification has so many exceptions it has no real value. For example, diamond have traditionally been considered precious gems, yet some sell for $100 a carat. You can see them (with enough magnification) as accent stones on inexpensive jewellery. On the other hand, garnet gems have traditionally been considered semiprecious gems, yet some sell in excess of $1,000 a carat, ten times the price of a low-quality diamond.

Referring to a set of gem types as “precious” and all other gems as “semiprecious” can be misleading, since it implies precious stones have inherently greater value. Professional gemmologists no longer use these terms. Consumers be wary if you encounter these descriptions.

Diamonds and Coloured Stones

Gems are also divided into two categories: diamonds and coloured stones. (Some dealers use the shorthand “colour” for coloured stones). Gem cutters and dealers use this gem classification system for two main reasons.

First, cutting diamonds requires special tools because these gems are harder than all others. With few exceptions, these tools aren’t suitable for cutting coloured stones. Therefore, gem cutters need two different sets of tools for handling both types of stones.
Second, diamonds and coloured stones are mined and distributed differently. Diamonds are one of the few gemstones with a consistent supply. Nevertheless, the diamond industry leads the general public to believe diamonds are incredibly rare In fact, there are coloured gems Far rare then diamonds .Why does this happen? A monopoly controls diamond sales and marketing. Those in charge are careful not to flood the market. Thus, diamonds maintain their value. This monopoly has also convinced the public that diamonds are the premier gemstones through excellent advertising.

In this gem classification system, all diamonds, whether clear or colourless, are still considered diamonds. Conversely, a colourless sapphire or topaz is still classified as a coloured stone.

Natural, Synthetic, and Imitation Gems

Another way to classify gems is as natural or synthetic. Natural stones, of course, form in nature. Stones created in labs can be subdivided further.

Syntheticrefers to materials that duplicate their natural counterparts. For example, synthetic emeralds, sapphires, and spinel’s share the physical and optical properties of the natural varieties. In many cases, distinguishing natural and synthetic stones is quite challenging.
Homoceratidmaterials have no natural counterparts. This category includes the synthetic garnets gadolinium gallium garnet (GGG) Andyttrium Aluminium Garnet (YAG).

For a long time, gemmologists considered cubic zirconia (CZ) a homoceratid gemstone. However, tiny CZ crystals not large enough to be used as gems have been found in nature. This discovery means CZ is a synthetic stone rather than a homoceratid.

Natural and synthetic materials can share the same properties yet still have considerable differences. The main difference is rarity. A natural gem usually takes millions of years to form. Plus, many people feel natural stones have aesthetic qualities not found in mass-produced materials. Value is another difference. Since natural gemstones are rarer and take longer to form, they’re more valuable than their synthetic counterparts. For this reason, distinguishing between naturals and synthetics is an essential skill for gemmologists.

A simulant or imitation gem is any material presented as some of kind of gem. For example, a natural white topaz sold as a diamond is an imitation. If sold as a white topaz, it’s a real, natural topaz. A CZ described as a cubic zirconia in a jewellery ad is not an imitation. In contrast, a CZ represented as a diamond is an imitation.

Organic and Inorganic Gems

Another approach to gem classification is to separate gems into organics and inorganics. Organics refer to gems whose formation involves living organisms. Amber, for example, began as tree sap. Various molluscs create Pearls. Hence, these gem materials are classified as organic.

The term inorganic covers everything else. So, everything in the mineral world falls into the inorganic classification. One notable political exception arises in the U.S. In this country, a gemstone can only be classified as a mineral if it was created geologically in the earth. Thus, lab-created stones, even though they have the same properties as their natural counterparts, can’t legally be described as minerals. For gem classification purposes, these lab-created gems have the same properties as their natural mineral counterparts. However, advertisements can’t describe them as minerals.

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