Understanding Gems to Make An Informed Online Jewelry Purchase

Precious gems are comprised of the traditional four precious stones which are rubies, diamonds, emeralds and sapphires. Their beauty is a matter of taste. What is considered a favorite today may be different a few decades from now.

The beauty of gems is made greater by shaping, polishing and cutting. Generally, beauty is considered first, followed by durability and rarity. A gem may be durable and rare, but without beauty it would not be as valued. The beauty of a diamond is the absence of color and its beauty. However, the beauty of an ruby or an emerald is their intense color. Wearing gemstone pieces of jewelry has been associated with status and wealth. If the gemstone is available in large amounts it is not considered to be as valuable as a rare gemstone.

A gem's reflection of light is it's source of color. Fine colored gems should not be so dark that they appear black, and should not be pale. A good depth of color is desired. The luster of a gem is the reflection of light from it's surface. Luster is improved when gems are polished. Reflection of light from the inside of the faceted gems is it's brilliance.

Gemstones are the raw materials that are used to make gems. Gemstones primarily are minerals. Some are rocks and others are the organic products of formerly living animals or plants. Ruby is a mineral, jade is derived from a rock, and amber and pearls are organic.

Minerals are often valuable gemstones because they can be converted into sparkling gems as a result of their transparency. Minerals can have interesting optical qualities and can form large transparent gemstones. Some minerals are symmetrical, and other minerals have no symmetry. When minerals are magnified for identification the symmetry of the crystals is most helpful. There seven systems of symmetry. For example garnets and diamonds have cubic symmetry and tourmaline has trigonal symmetry. Minerals which are perfectly symmetrical are very rare. This occurs because they need perfect growing conditions and sufficient space to grow without being constrained to become perfectly symmetrical.

A gemstone's durability is derived from its stability, toughness and hardness. A gem's toughness is it's resistance to cracking, chipping and breaking. Stability refers to a gem's resistance to structural or chemical changes from exposure to external elements. For example, pearls can be damaged by alcohol or perfume. A pearl necklace should always be worn after putting on hairspray or perfume. Some gemstones may fade when exposed to sunlight. Fortunately, most gems placed into jewelry can withstand normal wear with very little attention. A gem's resistance to scratching is its hardness. The Mohs scale ranks the hardness of 10 minerals based upon their ability to scratch each other. The scale is on a scale from 1 to 10 with a 1 being the softest. The Mohs scale rates diamonds as a 10.

A carat is the standard unit of mass for gems. Carat is abbreviated ct. They may sound similar but the words karat and carat have different meanings. Karats refers to a measurement of gold purity. The two terms are often confused.