What Is A Gemstone?

Most simply stated, the majority of gemstones are minerals. Important exceptions are pearl and coral, which are of animal origin, and jet and amber which are vegetable.

These minerals have been crystallized as a result of the high temperatures and pressures exerted by natural forces on the elements that form the earth's crust.

Of the more than 3000 minerals found on earth, only a small percentage qualify as "gemstones" due to their beauty, durability, colour and rarity. The most sought after are transparent gems, drops of pure colour cut from single crystals.

These gems were once divided into precious and semi-precious categories, but this is no longer true today.

Gem discoveries have added new varieties to the traditional selection of ruby, emerald and sapphire.

Some of these more unusual gemstones command higher prices than more well known gemstones due to their beauty and rarity.

For example, fine jade and fine opal, Tsavorite or alexandrite would be more valuable than lesser quality diamonds or emeralds.

The selection of fine-quality gemstones includes such stones as alexandrite, amber, amethyst, aquamarine, chrysoberyl, citrine, garnet, iolite, jade, kunzite, lapis lazuli, moonstone, opal, peridot, sugilite, spinel, tanzanite, topaz, tourmaline, tsavorite, turquoise and zircon.

Each of these gemstones has a particular charm and colour.

Characteristics and classification

The traditional classification in the West, which goes back to the Ancient Greeks, begins with a distinction between precious and semi-precious stones; similar distinctions are made in other cultures.

In modern usage the precious stones are diamond, ruby, sapphire and emerald, with all other gemstones being semi-precious.

This distinction is unscientific and reflects the rarity of the respective stones in ancient times, as well as their quality: all are translucent with fine color in their purest forms, except for the colorless diamond, and very hard,with hardnesses of 8-10 on the Mohs scale. Other stones are classified by their color, translucency and hardness.

The traditional distinction does not necessarily reflect modern values, for example, while garnets are relatively inexpensive, a green garnet called Tsavorite, can be far more valuable than a mid-quality emerald. Another unscientific term for semi-precious gemstones used in art history and archaeology is hardstone.

Use of the terms 'precious' and 'semi-precious' in a commercial context is, arguably, misleading in that it deceptively implies certain stones are intrinsically more valuable than others, which is not the case.

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