MELLITE: Germany (0.42)
Mellite is one of the most unusual of all gems, being an organic material formed by inorganic processes, just the reverse of the situation with pearls and coral. Crystals are additionally unusual in being pyroelectric (they generate an electric current when heated). Mellite is soft and very fragile. but is quite beautiful when cut. Truly this is one of the most interesting of the rare gemstones.
Mellite Value
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Mellite Information
| Data | Value |
| Name | Mellite |
| Crystallography | Tetragonal. Crystals prismatic, pyramidal; granular, nodular, massive. |
| Colors | Honey yellow, reddish, brownish, rarely white. |
| Luster | Resinous to vitreous. |
| Hardness | 2-2.5. |
| Density | 1.58-1.64. |
| Birefringence | 0.028-0.032. |
| Cleavage | Indistinct. Fracture conchoidal. Sectile. |
| Stone Sizes | Mellites are always small (1-3 carats) and may be quite transparent. |
| Luminescence | Dull white in SW, or medium light blue. Medium light blue in LW (Germany) or lemon yellow. May be weak brown in SW (USSR). |
| Spectral | Not diagnostic. |
| Formula | Al2C6(COO)6 ·18H2O (aluminum mellitate). |
| Pleochroism | Weak; yellow/yellow-brown. |
Optics: o=1.539—1.541; e=1.509—1.511.
Uniaxial (-).
Sometimes anomalously biaxial.
Occurrence: A secondary mineral in brown coals and lignites.
Artern and Bitterfeld, Germany; Paris Basin, France;
Czechoslovakia; Tula, USSR.
Comments: Mellite is one of the most unusual of all gems, being an organic material formed by inorganic processes, just the reverse of the situation with pearls and coral. Crystals are additionally unusual in being pyroelectric (they generate an electric current when heated). Mellite is soft and very fragile. but is quite beautiful when cut. Truly this is one of the most interesting of the rare gemstones.
Name: From the Latin word mel, meaning honey, in allusion to the color.
