Diamond type
Diamond type is a method of scientifically classifying diamonds by the level and type of their chemical impurities. Diamonds are separated into four types: Type Ia, Type Ib, Type IIa, and Type IIb. The impurities measured are at the atomic level within the crystal lattice of carbon atoms and so, unlike inclusions, require an infrared spectrometer to detect.
Diamond cut
Modified brilliants include the "marquise" or "navette" (French for "little boat", because it resembles the hull of a sailboat), "heart", triangular "trillion" (also "trillian" or "trilliant"), "oval", and the "pear" or "drop" cuts. These are the most commonly encountered modified brilliants;
"Oval-shaped diamonds" have been created and introduced by Lazare Kaplan way back in the 1960s. Usually noted to have 56 facets, the weight of such diamonds is estimated by measuring the length and width of the stone. A ratio of 1.33 to 1.66 provides a good traditional range of oval-shaped diamonds.
"Pear-shaped diamonds" are also known as the teardrop shape owing to their resemblance and is considered as a hybrid between the marquise cut and the round brilliant diamond. The stone has one end rounded while the other end is pointed. Pear shape diamonds can opt between varying length and width ratios for the ideal looking pear-shaped diamond. Length to width ratios between 1.45 and 1.75 are most common.