Clarity - how clear is my diamond?
Diamonds are rated for clarity on a scale that ranges from IF, or internally flawless, to I-3, or included level three. Flaws, or inclusions, may be black or white in color, and may appear as feathers, carbon spots, cracks, and so on. Flaws and inclusions are typically visible with the naked eye in the SI-2 range. The chart below details the clarity scale.
Color - how white is my diamond?
Diamonds are rated for their color in a scale that ranges from D (completely white) to Z. Yellowness or discoloration typically becomes visible in the I range. See chart below.
Cut/shape - what is the shape and how well-cut is my diamond?
Diamonds come in a variety of shapes, including round, square (princess-cut), oval, pear, emerald, cushion, and radiant. The chart below illustrates these shapes. Diamonds are renowned for their ability to transmit light and sparkle so intensely. We often think of a diamond's cut as shape (round, emerald, pear), but a diamond's cut grade is really about how well a diamond's facets interact with light. A diamond's cut is very important to the stone's final beauty and value. And of all the diamond qualities, it is the most complex and technically difficult to analyze. When a diamond's cut is graded, there are five grade levels: Excellent, Very Good, Good, Fair, and Poor.
Carat weight - how much does my diamond weigh?
Diamonds are rated for their size by their weight in carats. However, when judging how large a diamond appears, one must also consider its measurements (diameter, depth, etc.) as some diamonds may be unusually wide or narrow when viewed from the top. This is known as "facing up" big (or small). One carat is divided into 100 points: so, for example, a diamond weighing 50 points is .50 carats or 1/2 carat.