Gemstones, also known as precious or semi-precious stones, are some of the most beautiful and naturally created minerals in nature. The color, cut, clarity and carat weight are the four "Cs" that determine how precious a gem actually is. The "color" of a gemstone is made up of three aspects--hue, saturation and tone. The "cut" represents what is known as the "light performance," meaning how much the gem will sparkle when moved under a light at different angles. Inclusions in gems reduce their "clarity"--the clearest and most flawless stone will be the most expensive, as will a stone that is rare. The "carat weight" is also important, in that a carat is equal to 200 milligrams of the actual weight of a diamond.
The diamond is revered as the most precious gem in the world and is considered by crystal workers to be a highly evolved stone. It contains all the colors of the spectrum when light is refracted through it. Diamonds are associated with the attributes of purity, endurance and good fortune and are traditionally the stone of choice in a marriage. It is the hardest naturally occurring substance known to man, made up of crystalline forms of carbon, making it four times stronger than the second hardest substance. Diamond-cutters are used in precision engineering for their extreme hardness and durability.
Sapphires are a precious stone popularly thought of as an indigo blue color and more expensive than the other colors, such as green, yellow and pink. These colors occur when trace elements of impurities are present in their evolution. A sapphire is the crystalline form of aluminum oxide, a mineral variety of corundum. Sapphires can be determined in price by their geographic origin. The rarest and most expensive of the sapphires is the "Star Sapphire," which has an inclusion looking like a six-pointed star when held up to the light.
Blood-red and vividly colored rubies are the most sought-after of their kind and therefore, the most expensive. They come from the mineral corundum and unlike diamonds, rubies are all included with fine lines, so it's important to know what type of markings to look for. Make sure that inclusions are clearly defined and that they do not reach the surface of this precious gem, as this means it's more likely to crack along the lines on impact. The cloudier the ruby, the lesser the value. Ask the jeweler to look at your gem under a microscope to determine its flaws and value.
These precious stones are valuable, rare and belong to the beryl family. They are highly included with cracks and fissures, making their resistance to breakage poor. Emeralds are commonly shaped or polished rather than faceted due to their natural form. In order to command the highest price, emeralds should be medium to dark in color and vivid green. Gray or dull-green varieties can expect to ask less money. Emeralds are valued without microscopes, so if no inclusions are detected by the naked eye, they are considered flawless. Most emeralds are treated with oils to smooth out the fissures, which improves transparency. Many gems are lab-created, making them much more affordable, yet less desirable.