Jonassonite is a rare bismuth-gold sulfide mineral typically found as small grains within hydrothermal gold deposits. It is often identified via microprobe analysis due to its visual similarity to other metallic sulfide minerals found in association with gold.

Hardness

2.5-3

Mohs

Luster

Metallic

Streak

Black

Transparency

Opaque

mineralrare

Jonassonite

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

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Is this jonassonite?

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 jonassonite with a known reference. Jonassonite 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. Streak: black.
3
Read the luster
Hold the specimen under a strong light. Luster: metallic.
4
Match the color range
Compare against the expected color range: tin white.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: anhedral grains.

Often confused with

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

mineral

Bismuthinite

Mohs 2-2.5

How to tell apart: Streak differs, so Jonassonite leaves black, Bismuthinite leaves lead-gray.

How to tell apart: Streak differs, so Jonassonite leaves black, Tetradymite leaves pale steel-gray.

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Often found alongside jonassonite

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

All properties

Chemical formula: Au(Bi,Pb)₅S₄
Mohs hardness: 2.5-3
Density: 9.79 g/cm³
Colors: Tin white
Streak: Black
Luster: Metallic
Transparency: Opaque
Crystal system: Monoclinic
Crystal habit: Anhedral grains
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Detected in old mining dumps of the abandoned Nagybörzsöny deposit

Where rockhounds find jonassonite

Classic worldwide localities

Nagybörzsöny ore deposit, Börzsöny Mountains, Hungary (type locality)

Field-hunting tip

Where it forms: Detected in old mining dumps of the abandoned Nagybörzsöny deposit. If you start seeing native gold, bismuthinite, tetradymite in float, you are in the right ground. Typical habit: anhedral grains. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify jonassonite?+

Mohs hardness is 2.5-3. Luster: metallic. The streak is black. Common colors include tin white.

Where is jonassonite found?+

Notable localities include Nagybörzsöny ore deposit, Börzsöny Mountains, Hungary (type locality).

Is jonassonite safe to handle?+

Jonassonite contains lead. Contains bismuth, sulfur, and gold; as with most heavy metal-bearing sulfide minerals, avoid inhaling dust or ingesting particles and wash hands thoroughly after handling.

What rocks look like jonassonite?+

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

What minerals are found with jonassonite?+

Jonassonite commonly co-occurs with native gold, bismuthinite, tetradymite, pyrite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does jonassonite form in?+

Where it forms: Detected in old mining dumps of the abandoned Nagybörzsöny deposit. Working float back to the host body is the standard way to chase a fresh occurrence.

What is jonassonite used for?+

Jonassonite is used in collector.

Find jonassonite on the map

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