2. Color
Ideally, a diamond should be colorless like a drop of clear water. But, such diamonds are very rare and expensive. Most diamonds do have a tinge of yellow that is normally not visible to the naked eye. Increasing degrees of diamond color is measured on a scale of D to Z. D for clear diamonds and Z for diamonds with a lot of color.
Beyond "Z" is the range where the diamond's color is indeed very unrealistic and too dark for it to even be called a diamond. To grade a diamond’s color well-known diamonds with pure colors are used as a standard. A machine called the “Colorimeter" detects the amount of color in the diamond.

3. ClarityA diamond's clarity is determined by the number, nature, position, size and colour of internal inclusions of other metals or minerals in it. In simple words, we can say that a diamond that has no spots or traces of other elements and is absolutely clear and is a rare and beautiful piece of nature.
These irregularities that are found in most diamonds lower the price and value of these stones. Diamonds as we all know are mostly pure carbonbut sometimes during its formation minerals do get trapped in it that cools to form a blemish on the diamond .
Clarity is measured on a scale ranging from Pure to “heavily included” on a scale of 1-3. The clarity of a diamond is graded by professional diamond graders. The final clarity grade is usually determined by how easily the incursions are visible to the grader and to the naked eye of a lay man. Pure diamonds just shimmer and sparkle without any other elements in it.