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. Mellite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Mellite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: honey-yellow, brownish, reddish-yellow.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: bipyramidal crystals, massive, granular.
Often confused with
Mellite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Luster reads vitreous on Mellite and resinous on Amber.
How to tell apart: Sphalerite is the harder of the two (Mohs 3.5-4 vs. 2-2.5); streak differs — Mellite leaves white, Sphalerite leaves white to yellow-brown; luster reads vitreous on Mellite and resinous to submetallic on Sphalerite.
How to tell apart: Fluorite is the harder of the two (Mohs 4 vs. 2-2.5).
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
- Al₂C₁₂O₁₂·18H₂O
- Mohs hardness
- 2-2.5
- Density
- 1.6 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Tetragonal
- Crystal habit
- Bipyramidal Crystals, Massive, Granular
- Cleavage
- Indistinct
- Fluorescence
- Bright Blue Under SW UV
- Rarity
- Rare
- Uses
- Collector, Decorative
- Host rock
- Lignite and Brown Coal Deposits
- Typical price
- $20-150 for small specimens
Where rockhounds find mellite
Classic worldwide localities
- Artern, Germany
- Tula, Russia
- Csordakut, Hungary
- Kuznetsk Basin, Russia
Field-hunting tip
Look in lignite and brown coal deposits country — that is the host setting where mellite typically forms. If you start seeing lignite, kaolinite, gypsum in float, you are in the right ground. Field specimens usually show a bipyramidal crystals, massive, granular habit, so 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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