MELLITE

    Class : Organic compounds
    Subclass : -
    Crystal system : Tetragonal
    Chemistry : Al2C6(COO)6 16H2O
    Rarity : Rare

Mellite is a rare organic mineral appearing secondarily in lignite (and more rarely coal) deposits, its formation being linked to the organic activity of plants. From a chemical point of view, it is a natural calcium oxalate which can contain up to 45% water. Its name comes from the Greek meli (honey) in allusion to its honey-yellow color. Mellite is transparent to translucent, resinous to vitreous in luster, sometimes sectile, it has a yellowish brown to brownish color, sometimes also reddish and exhibits blue fluorescence in the short wavelengths of ultraviolet. Mellite appears in massive (grains, nodules) or pseudo-octahedral form, most often small. Its low density (1.6) allows it to be distinguished from minerals of similar appearance.

Main photo : 6 cm octahedral mellite from Csordakúti Mine, Hungary © Dávid Szabó

Mellite from Csordakúti Mine, Hungary © Peter Huber
Mellite from Csordakúti Mine, Hungary © Bruce Cairncross
Mellite fom Artern, Thuringia, Germany © Thomas Witzke
Fluorescent (SW) mellite from Csordakúti Mine, Hungary © Christopher O'Neill

Mellite in the World

Magnificent 5 cm gem-like pseudo-octahedral crystals, honey-colored, the most beautiful known, come from Tatabanya, near Budapest (Hungary). Large centimeter-sized crystals also come from the Malevka coal basin (Russia). Millimetric crystals of mellite occupy the cavities of silicified wood in the Polish deposits of Luschitz (Czech Republic) and the German deposits of Artern (Thuringia). It is known in relative abundance in the German lignite mines of Bitterfeld (Saxony) and Dransfeld (Lower Saxony).

Mellite in France

In France, mellite was reported at the beginning of the last century in the lignite of Auteuil, near Paris, associated with amber and marcasite.

Twinning

No twin known for this mineral species.

Fakes and treatments

No fakes recorded for this mineral species.


Hardness : 2 to 2.5
Density : 1.64
Fracture : Conchoidal
Streak : White

TP : Translucent to transparent
RI : 1.511 to 1539
Birefringence : 0.028
Optical character : Uniaxial -
Pleochroism : Low
Fluorescence : Yellow to blue

Solubility : Nitric acid, water

Magnetism : NoneRadioactivity : None

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