Törnroosite is an extremely rare platinum-tin-arsenic mineral typically found as microscopic inclusions within sulfide ores. It is primarily identified via electron microprobe analysis due to its small grain size and dark, non-distinct appearance.

Hardness

3-4

Mohs

Luster

Metallic

Streak

Black

Transparency

Opaque

mineralrare

Törnroosite

Hardness: 3-4
Luster: Metallic
Streak: Black
Transparency: Opaque

No image

Is this törnroosite?

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 törnroosite with a known reference. Törnroosite sits at Mohs 3-4 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Törnroosite leaves a black streak.
3
Read the luster
Hold the specimen under a strong light. Törnroosite typically shows a metallic luster.
4
Match the color range
Compare against the expected color range: black.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: anhedral grains.

Often confused with

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

mineral

Sperrylite

Mohs 6-7

How to tell apart: Sperrylite is the harder of the two (Mohs 6-7 vs. 3-4).

Often found alongside törnroosite

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

All properties

Chemical formula: Pt₆SnAs₂
Mohs hardness: 3-4
Density: 4.15 g/cm³
Colors: Black
Streak: Black
Luster: Metallic
Transparency: Opaque
Crystal system: Orthorhombic
Crystal habit: Anhedral Grains
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Copper-nickel Sulfide Deposits
Typical price: $50-500+ micro-mounts/thumbnail

Where rockhounds find törnroosite

Classic worldwide localities

Talnakh, Russia

Field-hunting tip

Look in copper-nickel sulfide deposits country — that is the host setting where törnroosite typically forms. If you start seeing sperrylite, platinum, chalcopyrite in float, you are in the right ground. Field specimens usually show a anhedral grains habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify törnroosite?+

Mohs hardness is 3-4. It typically shows a metallic luster. The streak is black. Common colors include black.

Where is törnroosite found?+

Notable localities include Talnakh, Russia.

How much is törnroosite worth?+

Typical asking prices fall in the range of $50-500+ micro-mounts/thumbnail. Quality, size, and provenance can move individual specimens well outside that range.

Is törnroosite safe to handle?+

It contains toxic constituents. Contains arsenic, handle with care and avoid inhalation of dust or ingestion. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like törnroosite?+

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

What minerals are found with törnroosite?+

Törnroosite commonly co-occurs with Sperrylite, Platinum, Chalcopyrite, Cubanite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does törnroosite form in?+

Törnroosite typically forms in copper-nickel sulfide deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is törnroosite used for?+

Törnroosite is used in collector.

Find törnroosite on the map

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