Fiedlerite is a rare lead chloride fluoride mineral primarily found in the ancient silver-lead slag dumps of Laurion, Greece. It typically occurs as transparent to translucent tabular crystals that can be difficult to distinguish from associated lead minerals like laurionite. Collectors prize it for its unique chemistry and historical significance as a secondary mineral resulting from seawater reaction with ancient slag.

Hardness

~3.5

Mohs

Luster

Adamantine

Streak

White

Transparency

Transparent

mineralrare

Fiedlerite

Hardness: ~3.5
Luster: Adamantine
Streak: White
Transparency: Transparent

Is this fiedlerite?

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 fiedlerite with a known reference. Fiedlerite sits at Mohs ~3.5, 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: colorless, white.
5
Look at form & habit
Crystal system: triclinic. Typical habit: tabular crystals.

Often confused with

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

Often found alongside fiedlerite

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

All properties

Chemical formula: Pb₃Cl₄F(OH)·H₂O
Mohs hardness: ~3.5
Density: 5.88 g/cm³
Colors: Colorless White
Streak: White
Luster: Adamantine
Transparency: Transparent
Crystal system: Triclinic
Crystal habit: Tabular crystals
Cleavage: {100}, good
Rarity: Rare
Uses: Collector
Host rock: Produced by reaction of halide-bearing seawater and metal-bearing slag

Where rockhounds find fiedlerite

Classic worldwide localities

Laurium, Greece
Baratti Beach, Tuscany, Italy
Argent Pb–Zn mines, about 100 km east of Johannesburg, Transvaal, South Africa

Field-hunting tip

Where it forms: Produced by reaction of halide-bearing seawater and metal-bearing slag. If you start seeing penfieldite, laurionite, phosgenite in float, you are in the right ground. Typical habit: tabular crystals. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify fiedlerite?+

Mohs hardness is ~3.5. Luster: adamantine. The streak is white. Common colors include colorless, white.

Where is fiedlerite found?+

Notable localities include Laurium, Greece; Baratti Beach, Tuscany, Italy; Argent Pb–Zn mines, about 100 km east of Johannesburg, Transvaal, South Africa.

Is fiedlerite safe to handle?+

Fiedlerite contains lead. Contains lead; wash hands thoroughly after handling and avoid inhaling dust or ingestion.

What rocks look like fiedlerite?+

Fiedlerite 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 fiedlerite?+

Fiedlerite commonly co-occurs with Penfieldite, Laurionite, Phosgenite, Cotunnite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does fiedlerite form in?+

Where it forms: Produced by reaction of halide-bearing seawater and metal-bearing slag. Working float back to the host body is the standard way to chase a fresh occurrence.

What is fiedlerite used for?+

Fiedlerite is used in collector.

Find fiedlerite on the map

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