Sundiusite is an extremely rare lead sulfate-chloride mineral first discovered in the famous Långban mines of Sweden. It typically occurs as small, clear, tabular crystals embedded in manganese-rich metamorphic rocks. Due to its extreme rarity, it is highly sought after by advanced mineral collectors specializing in lead species.

Hardness

Mohs

Luster

Adamantine

Streak

White

Transparency

Semitransparent

mineralrare

Sundiusite

Hardness: ~3
Luster: Adamantine
Streak: White
Transparency: Semitransparent

Is this sundiusite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch sundiusite with a known reference. Sundiusite sits at Mohs ~3, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: adamantine.
4
Match the color range
Compare against the expected color range: white, colorless.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: aggregates, plumose.

Often confused with

Sundiusite vs. its common look-alikes, and how to tell them apart in the field.

Often found alongside sundiusite

Minerals reported to co-occur with sundiusite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: Pb₁₀(SO₄)O₈Cl₂
Mohs hardness: ~3
Density: 7.0 g/cm³
Colors: White Colorless
Streak: White
Luster: Adamantine
Transparency: Semitransparent
Crystal system: Monoclinic
Crystal habit: Aggregates, plumose
Cleavage: {100}, perfect; {001}, possible
Rarity: Rare
Uses: Collector
Host rock: On fracture surfaces in a museum specimen of manganese ore from a metamorphosed Fe–Mn orebody

Where rockhounds find sundiusite

Classic worldwide localities

Långban, Värmland, Sweden

Field-hunting tip

Where it forms: On fracture surfaces in a museum specimen of manganese ore from a metamorphosed Fe–Mn orebody. If you start seeing blixite, braunite, hausmannite in float, you are in the right ground. Typical habit: aggregates, plumose. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify sundiusite?+

Mohs hardness is ~3. Luster: adamantine. The streak is white. Common colors include white, colorless.

Where is sundiusite found?+

Notable localities include Långban, Värmland, Sweden.

Is sundiusite safe to handle?+

Sundiusite contains lead. Contains lead, which is toxic if ingested or inhaled as dust. Wash hands thoroughly after handling and keep away from food.

What rocks look like sundiusite?+

Sundiusite is most often confused with Penfieldite, Laurionite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with sundiusite?+

Sundiusite commonly co-occurs with Blixite, Braunite, Hausmannite, Manganoan biotite, Calcite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does sundiusite form in?+

Where it forms: On fracture surfaces in a museum specimen of manganese ore from a metamorphosed Fe–Mn orebody. Working float back to the host body is the standard way to chase a fresh occurrence.

What is sundiusite used for?+

Sundiusite is used in collector.

Find sundiusite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.