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.
Diamonds as an investment
Old diamond jewellery in India, specially from the Mughal period, uses unfaceted diamonds. Mughal style jewellery has become popular in India recently featuring uncut diamonds termed "Polki" (which originally referred to a style of cleaving diamonds). The diamonds used in modern polki jewellery are low grade and do not have much investment value, even though polki jewellery can be expensive. The diamonds are backed by silver foil to allow light to reflect. The Kundan jewellery in India uses the same style, but it uses glass instead of diamonds.