Carat Weight

Carat weight is the weight of the diamond measured in carats. One carat is divided into 100 "points," so that a diamond of 75 points weighs 0.75 carats. Carat weight is the most obvious factor in determining the value of a diamond. But two diamonds of equal carat weights can have very different prices, depending on their quality. Diamonds of high quality can be found in all size ranges.

Color

The diamond color grading scale varies from totally colorless to light yellow. The differences between one diamond color grade and another are very subtle and difficult to distinguish.

D-F : Colorless: perfect or almost perfect color.

G-J : Near colorless: good to very good color, and this diamond may "face up" colorless when mounted, especially in white gold or platinum.

K-M : Light but noticeable yellow or brown tint. Not recommended for larger diamond stone purchases, especially in engagement rings.

Clarity

Diamond Clarity is a measure of a diamond's internal flaws and impurities. A diamond that is virtually free of interior or exterior inclusions (commonly referred to as flaws) is of the highest quality, for nothing interferes with the passage of light through the diamond. To determine a diamond's clarity, it is viewed under 10x magnification by a trained gemologist. Small inclusions neither mar its beauty nor endanger its durability.

Flawless - No internal or external flaws.

Internally Flawless - No internal flaws. Very rare and beautiful diamonds which are quite expensive.

VVS1, VVS2 - Very, Very Slightly Included: Very difficult to see inclusions under 10x agnification. An excellent quality diamond.

VS1, VS2 - Very Slightly Included: Inclusions are typically not visible to the unaided eye. Less expensive than the VVS1 or VVS2 grades. Even properly graded VS2 diamonds can have visible inclusions in very large sizes or diamonds that do not have many facets which make flaws more visible such as an emerald shape.

SI1, SI2 - Slightly Included: Inclusions are typically visible under 10x magnification, SI clarity diamonds are usually of the best value since inclusions are not always visible to the naked eye and prices are reasonable when compared to prices of the VS2 clarity and up grades. Some SI clarity diamonds do have visible inclusions and should be evaluated carefully.

SI3 - Slightly Included-Included: SI3 is an EGL grade and is not recognized by GIA or other gemological institutions. The SI3 clarity grade has been adopted by other labs as well. Typically an SI3 clarity grade would usually be given an I1 grade by the GIA.

I1 - Included: an I1 clarity diamond will have a visible flaw which can be seen with the naked eye, but there should only be one major flaw which is not too obvious. Overall the diamond should still look nice however I1 clarity grades vary quite a bit so one should be very careful when making a selection. If your budget only allows for an SI3 or I1 clarity diamond, be sure to examine it thoroughly before purchasing and make sure the inclusions do not detract from the overall beauty of the diamond.

I2, I3 - Included: These diamonds will have inclusions visible to the naked eye, and will have many black spots from the black inclusions and/or appear very cloudy or milky from the white inclusions, feathers and cracks.

Cut

Diamond Cut refers to how well proportioned the diamond is.  For example, what percentage of a diamonds diameter is its depth?  What are its various angles and how do they interact with one another?  While these may seem like esoteric questions, these are the essential factors that determine how beautiful your diamond will be.