Identifying Garnets Simplified
Identifying garnets by species is complicated. Learn how to use refractive index, hue, and absorption spectrum readings to simply the separation process.
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By Donald Clark, CSM IMG, updated on
Identifying Garnets Using Three Factors
You can use the refractive index (RI), hue, and absorption spectrum of your garnet specimen to make your identification.
| Species | RI | Hue | Absorption |
| 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 407 and or 430 nm. May show general absorption on blue end. |
| Pyrope | 1.714 1.742 | Purplish red through reddish orange and colorless | Usually a cut off at 440 to 445 nm and a broad band at 564 nm. None when colorless. Some with weak bands for almandine or spessartite components. |
| Pyrope/almandine | 1.742 1.785 | Reddish orange through red purple | Shows almandine spectra. |
| Almandine | 1.785 1.830 | Orangish red through purplish red. | Bands at 504, 520 and 573 nm. May have weak bands at 423, 460, 610 and 680-690. |
| Almandine/spessartite | 1.810 1.820 | Reddish orange through orange red. | Cut off to 435, bands at 460, 480, 504, 520, and 573 nm. Merging of |
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