Green (hue / variety / modifier): Abbreviated (G). A perceived colour resembling the peel of an unripe lime (Citrus aurantifolia) or a healthy grass lawn or the gemstone emerald. Green is one of the spectrum colours, positioned between blue and yellow, in the 490 nm to 560 nm wavelength region. Green is also spoken of as being a cool colour when tinged with blue, and a warm colour when tinged with yel low. In the diamond trade, green (G) represents one of the basic twelve colour varieties. Green diamonds can also contain secondary colour modifiers such as grayish green (gy-G), bluish green (b-G), blackish green (bk-G) , olivish green (ol-G), and yellowish green (y-G) . Green can also occur as a secondary colour modifier in other colour varieties such as greenish blue (g-B), green-yellow (G-Y), etc. The range of colour tone for green diamonds is variable in both lightness and saturation, resulting in pale (lettuce) green, bright (emerald) green, dull (laurel) green, and deep (bottle) green colours. Popular names for different mixtures of green are: absinthe, ajer-laut, apple, bottle, bud, celery, emerald, forest, grass, honeydew, jade, laurel, leaf, lettuce, lime, mint, moss, pea, pistachio, sea, sea foam, siskin, spinach, spruce, sultana, and teal. The majority of green diamonds occur in pale or dull tones with light through dark (Lit) and weak through moderate (Sat). These diamonds owe their inherent green body colours to the absorption of various wavelengths of red light (see GR1 center) . Diamonds in this group pose the greatest challenge to modern research, which currently has not yet devised a definitive procedure for separating natural from artificially irradiated (treated) greens. Thus the colour origin of certain green diamonds is labeled as undeterminable (e.g ., Christie’s NY Oct 1988 Lot 400; NY Apr 1989 Lot 270; NY Oct 1989 Lots 201 , 203 & 538). A few diamonds in the bluish green to pure green range have been identified as natural (e .g., Christie’s NY Oct 1992 Lot 727 and Sothebys NY Apr 1992 Lot 437) based on studies of known natural green diamonds in museums; however, considerable research is still under way. There are also green diamonds (Sotheby’s NY Apr 1988 Lot 7; NY Apr 1995 Lot 597) that are of natural colour that exhibit bright tones with light through medium (Lit) and moderate through strong (Sat). This group of green diamonds owe their bright body colours to a combination of absorption and fluorescence. When viewed under daylight, they typically exhibit a strong lime green fluorescent glow in addition to their inherent green body colour