Colour : The majority of engagement rings are a very white coloured diamond. Colours are graded from D (colourless and very rare), but most diamonds are around a F-H.
Clarity : Being natural, there will be imperfections in the diamond. The less imperfections, the greater the clarity and the more light is reflected from the diamond, causing it to "sparkle". Naturally, more clarity increases its value. Perfectly flawless diamonds with no internal flaws or surface blemishes are very hard to find as they are extremely rare.
Cut : There are many different ways to cut a diamond and the type of cut effects the sparkle of the diamond. The cut that produces the most sparkle is the round cut (also known as brilliant), while radiant and princess cuts are good at hiding flaws. Other cuts including square, emerald, pear, marquise, cushion, ssscher, and heart-shaped.
Carat : This is the weight of the diamond. Big is not always better
You need to consider all 4 C’s before choosing your diamond.