Franckeite is a complex lead-tin sulfide mineral often found in distinctive thin, flexible, tabular, or fan-shaped crystals. It is primarily sourced from tin-bearing hydrothermal deposits in Bolivia and is highly prized by collectors for its unique layered crystal structure.

Hardness

2.5-3

Mohs

Luster

Metallic

Streak

Black

Transparency

Opaque

mineralrare

Franckeite

Hardness: 2.5-3
Luster: Metallic
Streak: Black
Transparency: Opaque

Is this franckeite?

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 franckeite with a known reference. Franckeite sits at Mohs 2.5-3, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Franckeite leaves a black streak.
3
Read the luster
Hold the specimen under a strong light. Franckeite typically shows a metallic luster.
4
Match the color range
Compare against the expected color range: black, dark gray.
5
Look at form & habit
Crystal system: triclinic. Typical habit: tabular crystals, foliated masses, radiating aggregates.

Often confused with

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

How to tell apart: Streak differs, so Franckeite leaves black, Galena leaves lead-gray.

Often found alongside franckeite

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

All properties

Chemical formula: (Pb,Sn)₆FeSn₂S₁₄
Mohs hardness: 2.5-3
Density: 5.5-5.9 g/cm³
Colors: Black Dark Gray
Streak: Black
Luster: Metallic
Transparency: Opaque
Crystal system: Triclinic
Crystal habit: Tabular Crystals, Foliated Masses, Radiating Aggregates
Cleavage: Perfect Basal
Rarity: Rare
Uses: Collector, Geological Study
Host rock: Hydrothermal Veins
Typical price: $20-150 for thumbnail to small cabinet specimens

Where rockhounds find franckeite

Classic worldwide localities

Chocaya, Bolivia
Tasna, Bolivia
Oruro, Bolivia
San Jose Mine, Bolivia

Field-hunting tip

Look in hydrothermal veins country, the host setting where franckeite typically forms. If you start seeing cylindrite, cassiterite, wurtzite in float, you are in the right ground. Field specimens usually show a tabular crystals, foliated masses, radiating aggregates habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify franckeite?+

Mohs hardness is 2.5-3. It typically shows a metallic luster. The streak is black. Common colors include black, dark gray.

Where is franckeite found?+

Notable localities include Chocaya, Bolivia; Tasna, Bolivia; Oruro, Bolivia; San Jose Mine, Bolivia.

How much is franckeite worth?+

Typical asking prices fall in the range of $20-150 for thumbnail to small cabinet specimens. Quality, size, and provenance can move individual specimens well outside that range.

Is franckeite safe to handle?+

It contains toxic constituents. Contains lead and tin; wash hands thoroughly after handling and avoid inhaling dust. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like franckeite?+

Franckeite is most often confused with Cylindrite, Galena, Teallite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with franckeite?+

Franckeite commonly co-occurs with Cylindrite, Cassiterite, Wurtzite, Stannite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does franckeite form in?+

Franckeite typically forms in hydrothermal veins. Working float back to the host body is the standard way to chase a fresh occurrence.

What is franckeite used for?+

Franckeite is used in collector, geological study.

Find franckeite on the map

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