What is Mellite?
Mellite is a mineralogical surprise: a bright honey-yellow crystal can grow in a dark lignite seam through chemistry involving organic acids and aluminium. It is an excellent conversation piece for a collection that goes beyond silicates and ores.
Mineralogy and crystal structure
Reference formula: Al2C6(COO)6·16H2O. Mellite is a rare hydrated aluminium mellitate and one of the classic organic minerals. Its tetragonal crystals are soft and light, and its occurrence in coal makes geological context essential for identification. Mellite is classified with organic minerals and has a tetragonal crystal system. Typical hardness is 2–2.5 on the Mohs scale and specific gravity is approximately 1.6–1.7.
Colour, lustre and habit
Typical colours include honey-yellow, yellow, brown, orange. The usual tabular, prismatic, granular habit and resinous, vitreous lustre help describe a specimen, but colour alone is not diagnostic.
Formation and notable localities
Mellite forms in or is associated with lignite and brown-coal deposits where organic matter reacts with aluminium-bearing fluids. Important documented localities include Hungary, Germany, Austria, the Czech Republic, Russia and Japan.
Honey-yellow crystals from ancient coal
Mellite is a mineralogical surprise: a bright honey-yellow crystal can grow in a dark lignite seam through chemistry involving organic acids and aluminium. It is an excellent conversation piece for a collection that goes beyond silicates and ores.
Collecting and care
Soft and water-bearing: keep dry, cool and protected from abrasion or prolonged humidity.
