The most complicated part of identifying garnets is distinguishing between the species. The gems in the almandine, pyrope, and spessartite series are particularly difficult separations. However, the following chart will simplify the process once you’ve done your preliminary identification and are sure you’re dealing with a garnet stone.
Identifying Garnets Using Three Factors
RI is useful for distinguishing pyrope and grossular, since their values are much lower than the rest. For identifying garnets of other species, you’ll need a combination of RI, hue, and absorption spectrum evaluations.
|Andradite||1.880 1.895||Very slightly yellowish green through orangey yellow||None except demantoid, which shows a cut off at 440-445 nm. May have bands at 618 and 634. Demantoid may have thin bands at 685 and 690.|
|Grossular||1.730 1.760||All colors, including colorless, except blue.||None except highly saturated orange which show bands at|