The 4 C's
Diamond carat weight is the measurement of how much a diamond weighs. A metric "carat" is a small unit of measurement equal to 200 milligrams. Each carat can be subdivided into 100 points. A 0.75 carat diamond is the same as 75 points or 3/4 carat diamond. Carat weight doesn't always tell the full story when referring to a diamonds size. It is also important to look at the measurements or spread of a diamond. This will tell you how big or small it will face up in relation to its weight.
A diamonds color refers to how colorless a diamond is. The Gemological Institute of America (GIA) grades diamonds on a scale from D-Z. D,E, and F make up the colorless range while, G, H, I, and J make up the near color less range. The closer you get to D, the more valuable the stone is. The difference between colors is very subtle and can be difficult to see from an untrained eye, however the slight differences make a big difference in value and price.
Diamonds contain unique birthmarks, either internal (inclusions) or external (blemishes) because of the extreme heat and pressure they face when formed deep within the earth. Clarity refers to the absence or presence of these inclusions and blemishes. Many inclusions and blemishes are too tiny to be seen by the naked eye. A 10x magnification loop is used to view inclusions. Where inclusions are located on a diamond is extremely important and can greatly affect its value. Inclusions off to the side, ones that can be hidden by a prong are more desirable than inclusions in the middle or top of a diamond that could impact the brilliance of the stone.
The cut of a diamond refers to its ability to transmit light and sparkle intensely. Diamonds need to be cut so precisely so their facets will bounce light back and forth and shoot it up through the top of the stone. If a stone is cut too deep or shallow, there will be less brilliance and fire. Round diamondsare the only shape that GIA gives a cut grade.