Crystallographic defects in the crystal lattice of diamond are common; they may be the result of extrinsic substitutional impurities, or intrinsic (interstitial and structural) anomalies. All diamonds possess crystal lattice defects of some sort; the defects themselves may be either anthropogenic or natural, epigenetic or syngenetic. The material properties of diamond are affected by these defects and determine to which type a diamond is assigned; the most dramatic effects are on a diamond's color and semiconductivity, as explained by the band theory.
The defects can be detected by different types of spectroscopy, including ESR, photoluminescence in ultraviolet light, and absorption of infrared light. The resulting absorption spectrum can then be analyzed, identified, and used to separate natural from synthetic or enhanced diamonds.