The shape of a diamond has a big effect on price with the most expensive being marquise shape, then brilliant, pear, oval, emerald, heart, radiant, and princess. Diamonds often have tints of yellow but may also display tints of gray, green, or brown. The more color present the less expensive the diamond. The exception would be diamonds with color so intense they are consider to be fancy in color. Refers to the amount and type of inclusions in a diamond.
Some inclusions are minute diamond crystals inside the larger crystal.
Other types of inclusions include carbon, and cracks or cleavages in the diamond. Cleavages that are small and internal are not as serious as those that break the surface which could cause damage to the diamond should it be struck there. From Flawless to VS1 it is very difficult if not impossible for the average person to see the inclusions even with the aid of a 10x loupe. SI1 is a very good clarity that will almost always require a loupe. Some diamonds with a clarity rating of I1 may even be eye clean and acceptable for an engagement ring.