A diamond's cost is based on the characteristics known as the "4 C's". Clarity, Color and Cut are the quality elements which together with the Carat Weight determine the value of a stone. The closer a diamond grades to the left of one or all of these scales the rarer and the more costly it will be.

Carat Weight
Carat is the unit of weight for all gemstones. One carat is subdivided into 100 "points". Therefore a diamond measuring 75 points is 3/4 carat in weight, or 0.75ct. There are five carats in a gram.

Cut
Cut, sometimes the forgotten "C", ensures that a given stone has maximum brilliance and sparkle which would not be the case were the stone cut for weight alone.

Clarity
A diamond's clarity is determined by the number, nature, position, size and colour of internal characteristics called "inclusions" and surface features called "blemishes". These show themselves as the various characteristics which make up the clarity of a diamond (included crystals, feathers, clouds etc). Clarity is measured on a scale ranging from pure (flawless) to heavily included (I-3)

Clarity Grading Scale (GIA)
Flawless		VVS1	VVS2	VS1	VS2	SI1	SI2	I1	I2	I3
Internally		Very, Very		Very Slightly		Sligthly		Imperfect
Flawless		Slightly Included		Included		Included

Color
Ideally, a diamond should have no colour at all, like a drop of spring water. Increasing degrees of body color are measured on a scale ranging from no colour at all (D) to deeply coloured (Z). Beyond "Z" is the range where the diamond's color is vivid and rich, called "fancy colors". Diamonds of known color are used as comparison stones for color grading.

Color Grading Scale (GIA)
D	E	F	G	H	I	J	K	L	M	N	O	P	Q	R	S	T	U	V	W	X	Y	Z
			Near				Faint			Very Light					Light								Fancy
Colorless			Colorless				Yellow			Yellow					Yellow								Yellow