Diamond is the most romanticized and heavily marketed of all gemstones. Nearly every jewelry establishment handles diamonds, even if it has no other gemstones in stock. The annual world production of diamonds is on the order of 10 tons. Of course, only a small percentage of this is gem quality, but diamond of very fine quality is nowhere near as scarce as equivalently high quality ruby or emerald.
Diamonds are the among nature’s most precious and beautiful creations.
It is a mineral composed of pure carbon and It is the hardest naturally occurring substance known; it is also the most popular gemstone. Because of their extreme hardness, diamonds have a number of important industrial applications.
Diamonds are the hardest natural substance known to man. They are 58 times harder than the next hardest mineral on Earth. The only substance that can scratch a diamond is another diamond. A diamond over one carat in weight is one in a million. 

Characteristics of diamonds:

The four Cs are the four characteristics traditionally used to determine the quality and value of a diamond: carat, cut, clarity, and color. The characteristics of a diamond are graded and categorized by the diamond industry to establish its retail value.

 

• Color:

Understanding what diamond color means helps in choosing the right diamond. Interestingly, the diamond color evaluation of most gem-quality diamonds is based on the absence of color. A chemically pure and structurally perfect diamond has no hue, like a drop of pure water, and consequently, a higher value. GIA’s D-to-Z diamond color-grading system measures the degree of colorlessness by comparing a stone under controlled lighting and precise viewing conditions to masterstones of established color value.

Many of these diamond color distinctions are so subtle that they are invisible to the untrained eye; however, these distinctions make a very big difference in diamond quality and price. Hence, it is important to get a GIA expert’s opinion in evaluating the best color for your diamond.

 

*GIA color grades. Image by Open School of Diamond Gemology. Licensed under CC By 3.0.

*GIA examples. Image by GIA educational website       

  

• Clarity:

Diamond clarity refers to the absence of inclusions and blemishes. Diamonds without these birthmarks are rare, and rarity affects a diamond's value. Using the GIA International Diamond Grading System, diamonds are assigned a clarity grade that ranges from flawless (FL) to diamonds with obvious inclusions (I₃).

 

*Image by GIA educational website  

• Cut:

Cut describes how the diamond's surface has been cut into many tiny facets. The orientation and size of the facets affect how the light will pass through the diamond. This influences how much the diamond will sparkle and how large it will appear. Diamond cut grades range from excellent to poor.

       

The GIA cut grade system includes ratings of Excellent, Very Good, Good, Fair and Poor. GIA does not assign an Ideal cut and an Excellent rating is their highest grade.

Where GIA evaluates a round brilliant diamond's cut based on seven components – brightness, fire, scintillation, weight ratio, durability, polish and symmetry.

 

• Carat Weight:

To put it simply, diamond carat weight measures how much a diamond weighs. 

A metric “carat” is defined as 200 milligrams. Each carat is subdivided into 100 ‘points.’ This allows very precise measurements to the hundredth decimal place. A jeweler may describe the weight of a diamond below one carat by its ‘points’ alone. For instance, the jeweler may refer to a diamond that weighs 0.25 carats as a ‘twenty-five pointer.’ Diamond weights greater than one carat are expressed in carats and decimals. A 1.08 carat stone would be described as ‘one point oh eight carats.’

 

All else being equal, diamond price increases with diamond carat weight because larger diamonds are rarer and more desirable. However, two diamonds of equal carat weight can have very different values (and prices) depending on three other factors of the diamond 4Cs: Color, Clarity, Carat and Cut.

Actual Size On Hand:

If your hands are smaller than a 6.5 ring size you might want to consider a 1.0 carat or a stone that is under 1.50 carats. However, if your hands are larger than a 6.5 ring size you can go with something larger, like a 1.50-2.0.

GIA Report 

A GIA report is a worldwide recognized diamond grading report. A GIA diamond grading report breaks down the four characteristics of a diamond. It reports a scientific and unbiased assessment stating the diamond's authenticity. It also states if the diamond has undergone any treatments.

 

*GIA sample report