Cianciulliite is a rare manganese zinc hydroxide mineral primarily found in the Långban mining district of Sweden. It typically occurs as small, delicate, dark brown to reddish brown tabular crystals formed in the cavities of metamorphosed manganese ores. Because of its rarity and fragile nature, it is highly sought after by advanced mineral collectors specializing in Swedish minerals.
Is this cianciulliite?
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 cianciulliite with a known reference. Cianciulliite sits at Mohs ~2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: red brown.
- 3Read the lusterHold the specimen under a strong light. Luster: adamantine to vitreous; dull to pearly on cleavage.
- 4Match the color rangeCompare against the expected color range: dark brown, dark reddish brown, reddish brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: lath, tabular.
Often confused with
Cianciulliite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Cianciulliite leaves red brown, Pyrochroite leaves white; luster reads adamantine to vitreous; dull to pearly on cleavage on Cianciulliite and pearly on cleavages on Pyrochroite.
How to tell apart: Hausmannite is the harder of the two (Mohs 5.5 vs. ~2); streak differs, so Cianciulliite leaves red brown, Hausmannite leaves dark reddish brown; luster reads adamantine to vitreous; dull to pearly on cleavage on Cianciulliite and submetallic on Hausmannite.
Often found alongside cianciulliite
Minerals reported to co-occur with cianciulliite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Mg₂MnZn₂(OH)₁₀·2-4H₂O
- Mohs hardness
- ~2
- Density
- 2.87 g/cm³
- Streak
- Red brown
- Luster
- Adamantine to vitreous; dull to pearly on cleavage
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Lath, tabular
- Cleavage
- Perfect on {100}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A very rare mineral on a museum specimen, typical of material from secondary veins in a metamorphosed stratiform zinc orebody
Where rockhounds find cianciulliite
Classic worldwide localities
- Franklin, Sussex Co., New Jersey, USA
Field-hunting tip
Where it forms: A very rare mineral on a museum specimen, typical of material from secondary veins in a metamorphosed stratiform zinc orebody. If you start seeing willemite, zincite, cahnite in float, you are in the right ground. Typical habit: lath, tabular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify cianciulliite?+
Where is cianciulliite found?+
What rocks look like cianciulliite?+
What minerals are found with cianciulliite?+
What kind of rock does cianciulliite form in?+
What is cianciulliite used for?+
Find cianciulliite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
