Gemstone

From ArticleWorld


Gemstones are of various kinds, shapes, and characteristics and differ in matters of hardness, weight, size, color and luster. These mineral rocks are 'the bones of Mother Earth'. Gemstones in high demand are often cut and polished, either to use in jewelry or simply for collectible purposes. Some gemstones are deemed organic, as they contain fossilized organic matter within them. Amber is such a stone because it is comprised of fossilized tree resins. Jet, a form of coal, is another example.

Some stones are truly beautiful but much too soft and fragile to be used in jewelry, such as the single-crystal rhodochrosite. These stones are often displayed in museums. Whatever the kind of gemstone, they are all precious and are all suitable for some type of decorative purpose.


Characteristics and classifications

Gemstones are distinguished and grouped in a variety of ways.

Gemstones cannot be found just anywhere. They are rare minerals and are found only after much excavation. The point where a gemstone is found is called 'occurrence'. Gemstones are individually distinguished by gemologists using technical specifications. One of the most common and widely used modes of distinction is chemical composition. Each stone is termed after its chemical composition. For example, the diamond is made of carbon (C) and the ruby of aluminum oxide (Al2O3 ).

Gemstones are also classified on the basis of their crystal system if they are crystal in nature. Another way of distinguishing gemstones is by determining the form in which they are originally found. This is known as a gemstone's 'habit'. For instance, the diamond belongs to a cubical crystal system and is found in octahedron.

Gemstones are also grouped under varieties, species and groups. Rubies, for example, are grouped under red variety or species. Corundum falls under spinel or hematite. Emerald (green), aquamarine (blue), bixbite (red), goshenite (colorless), heliodor (yellow), and morganite (pink) are all varieties of one mineral called beryl.

Gems have certain typical characteristics of their own. They can be characterized by their refractive index, dispersion, hardness, specific gravity, cleavage, fracture and, most importantly, luster.

Some may be distinguished by their double refraction capacity, while others may have effective luminescence or distinctive absorption spectrum. However, any flaws on these gems are caused by inclusions.

Value

Gemstones may be valued for their scarcity, beauty, history or mystical qualities.

Gemstones are prized because they are attractive, rare, durable and always in fashion. They are often used in beautiful and valuable jewelry, and are appreciated because they are pleasing to the eye. Some factors that place gemstones in high demand are desirable color, size, unusual optical phenomena, natural crystal structure and fossilized inclusions that make for unique pieces to possess. The diamond is the hardest and therefore most valuable of all gemstones. Precious gemstones were once referred to as 'cardinal gems' because of their ecclesiastical, devotional and ceremonial use throughout history.

The rarest of gemstones include andalusite, axinite, cassiterite, clinohumite and iolite. These gemstones are so unusual they are often recognized by connoisseurs only.

Synthetic and artificial gemstones

Synthetic gemstones are produced largely for their lower cost.

Gemstones are commonly created in labs to appear similar to genuine ones for various reasons, one of which is their substantially lower cost. Imitation diamonds are called cubic zirconia and are made of zirconium oxide. Although gemstones such as rubies, sapphires and diamonds are often manufactured in labs, they possess nearly all the attributes of the authentic stones, but cost much less.