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 — 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 — that is 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.