Mellite is a rare organic mineral known as the aluminum salt of mellitic acid, typically forming beautiful honey-colored crystals within coal seams. It is remarkably soft and lightweight, often associated with lignite deposits where it forms by the action of groundwater on plant material. Collectors highly prize these crystals for their aesthetic clarity and intense fluorescence under ultraviolet light.
Is this mellite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch mellite with a known reference. Mellite sits at Mohs 2-2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: resinous to vitreous.
- 4Match the color rangeCompare against the expected color range: brown, brownish white, colorless, yellow, golden brown.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: crystalline, massive.
Often confused with
Mellite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Sphalerite is the harder of the two (Mohs 3.5-4 vs. 2-2.5); streak differs, so Mellite leaves white, Sphalerite leaves pale brown to pale yellow and white.
How to tell apart: Fluorite is the harder of the two (Mohs 4 vs. 2-2.5); luster reads resinous to vitreous on Mellite and vitreous; dull when massive on Fluorite.
Often found alongside mellite
Minerals reported to co-occur with mellite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Al₂C₆(COO)₆·16H₂O
- Mohs hardness
- 2-2.5
- Density
- 1.64 g/cm³
- Streak
- White
- Luster
- Resinous to vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Tetragonal
- Crystal habit
- Crystalline, massive
- Cleavage
- {023}, indistinct
- Fluorescence
- Blue under SW and LW UV
- Rarity
- Rare
- Uses
- Collector, Decorative
- Host rock
- An uncommon secondary mineral in brown coal and lignite deposits, aluminum typically derived from clay
Where rockhounds find mellite
Classic worldwide localities
- Artern, Thuringia, and near Bitterfeld, Saxony-Anhalt, Germany
- Lušice, near Bílina, Valchov, and Boskovice, Czech Republic
- Csordakút mine, Tatabánya, Hungary
- Malevka, Bogoroditsk district, southeast of Tula, Russia
Field-hunting tip
Where it forms: An uncommon secondary mineral in brown coal and lignite deposits, aluminum typically derived from clay. If you start seeing lignite, kaolinite, gypsum in float, you are in the right ground. Typical habit: crystalline, massive. Train your eye for that shape before scanning the outcrop.
Common questions
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Find mellite on the map
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