Like a snowflake if there is suitable atmosphere like time, place and a good chance, then a diamond is created. It is not necessary that two diamonds would be the same. We couldn’t judge the diamond until the middle of twentieth century. The reason is there was no suitable standard to judge the diamonds. The first standard to describe diamonds (including Color, Carat Weight, Cut, and clarity) was created by GIA, which was accepted globally. Today, anywhere in the world, if we have to find the quality of any diamond, we use 4Cs method.
There are two very important things about 4Cs while creating diamond which are:

The carat is the measure of the actual weight of the diamond. The greater the weight of a diamond, the more rare it is. Carat weight is not always the same as size appearance. The choice of how a diamond is cut is a critically important factor in determining whether a diamond “looks its weight”. Stones that have too high a depth percentage carry more weight in the height of the diamond where it does not add to the visual size appearance. The price per carat increases with carat weight, since larger diamonds are both rarer and more desirable for use as gemstones.

The finest quality as per color grading is totally colorless, which is graded as “D” color diamond across the globe, meaning it is absolutely free from any color.The next grade has a very slight trace of color, which can be observed by any expert diamond valuer, these are graded as E color or F color diamonds. Diamonds which show very little traces of color are graded as G or H color diamonds. Slightly colored diamonds are graded as I or J or K color. A diamond can be found in any color in addition to colorless. Some of the colored diamonds, such as pink, are very rare. Diamonds may contain small traces of color within the crystal structure, most often tints of yellow or brown. Differences in the color are subtle and difficult to see with the untrained eye. The less tint of color in a diamond, the more rare it is.

The clarity of a diamond refers to the presence of internal “inclusions” occurring naturally within the crystal structure. Almost all diamonds have some degree of inclusions, but in the higher quality diamonds, inclusions are not visible to the naked eye. The higher the clarity of a diamond, the more rare it is. The number, size, color, relative location, orientation, and visibility of inclusions can all affect the relative clarity of a diamond. Most inclusions present in gem-quality diamonds do not affect the diamonds’ performance or structural integrity. According to the Gemological Institute of America (GIA) diamond clarity rating can be divided into the following six:

Diamond cutting is the art and science of creating a gem-quality diamond out of mined rough. The cut of a diamond describes the manner in which a diamond has been shaped and polished from its beginning form as a rough stone to its final gem proportions. Cut refers to the angles and proportions of a diamond and determines how brilliant, beautiful and valuable the diamond is. Cut is the only aspect of a diamond determined by the skill and artistry of the craftsman’s hand. There are mathematical guidelines for the angles and length ratios at which the diamond is supposed to be cut in order to reflect the maximum amount of light. Round brilliant diamonds, the most common, are guided by these specific guidelines, though fancy cut stones are not able to be as accurately guided by mathematical specifics.