Roymillerite is a rare lead-magnesium silicate mineral known almost exclusively from the famous Långban mine in Sweden. It typically forms attractive, thin platy crystals with a distinct pearly luster that are highly sought after by advanced collectors of rare minerals.
Is this roymillerite?
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 roymillerite with a known reference. Roymillerite sits at Mohs 3-4 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Roymillerite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Roymillerite typically shows a pearly luster.
- 4Match the color rangeCompare against the expected color range: pink, violet-pink.
- 5Look at form & habitCrystal system: triclinic. Typical habit: platy crystals.
Often confused with
Roymillerite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Manganhumite is the harder of the two (Mohs 6-6.5 vs. 3-4); luster reads pearly on Roymillerite and vitreous to resinous on Manganhumite.
How to tell apart: Katoptrite is the harder of the two (Mohs 5-6 vs. 3-4); streak differs — Roymillerite leaves white, Katoptrite leaves black; luster reads pearly on Roymillerite and metallic on Katoptrite.
Often found alongside roymillerite
Minerals reported to co-occur with roymillerite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Pb₂₄Mg₉(Si₁₂O₃₀)(Si₂O₇)(OH)₃₀O₄
- Mohs hardness
- 3-4
- Density
- 2.88 g/cm³
- Colors
- Streak
- White
- Luster
- Pearly
- Transparency
- Translucent
- Crystal system
- Triclinic
- Crystal habit
- Platy Crystals
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Metamorphic Manganese-iron Deposits
- Typical price
- $100-500 thumbnail, $500+ cabinet
Where rockhounds find roymillerite
Classic worldwide localities
- Långban, Filipstad, Värmland, Sweden
Field-hunting tip
Look in metamorphic manganese-iron deposits country — that is the host setting where roymillerite typically forms. If you start seeing långbanite, hausmannite, dolomite in float, you are in the right ground. Field specimens usually show a platy crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find roymillerite on the map
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