Rheniite is a exceptionally rare rhenium sulfide mineral that primarily occurs in high-temperature volcanic fumaroles. It typically forms thin, metallic, platy crystals that closely resemble molybdenite, but it is unique for being the only mineral where rhenium is an essential constituent. Most specimens are sourced from the Kudryavy Volcano in the Kuril Islands, where it was first discovered.

Hardness

1.5-2

Mohs

Luster

Metallic

Streak

Black

Transparency

Opaque

mineralrare

Rheniite

Also: Rhenite

Hardness: 1.5-2
Luster: Metallic
Streak: Black
Transparency: Opaque

Is this rheniite?

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 rheniite with a known reference. Rheniite sits at Mohs 1.5-2 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Rheniite leaves a black streak.
3
Read the luster
Hold the specimen under a strong light. Rheniite typically shows a metallic luster.
4
Match the color range
Compare against the expected color range: black, gray.
5
Look at form & habit
Crystal system: hexagonal. Typical habit: platy crystals, scales, or massive aggregates.

Often confused with

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

mineral

Molybdenite

Mohs 1-1.5

How to tell apart: Streak differs — Rheniite leaves black, Molybdenite leaves greenish-gray.

How to tell apart: Streak differs — Rheniite leaves black, Tungstenite leaves gray-black.

Compare →

Often found alongside rheniite

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

All properties

Chemical formula: ReS₂
Mohs hardness: 1.5-2
Density: 7.5 g/cm³
Colors: Black Gray
Streak: Black
Luster: Metallic
Transparency: Opaque
Crystal system: Hexagonal
Crystal habit: Platy Crystals, Scales, Or Massive Aggregates
Cleavage: Perfect Basal
Rarity: Rare
Uses: Collector, Research
Host rock: Fumarole Deposits
Typical price: $100-500+ per specimen

Where rockhounds find rheniite

Classic worldwide localities

Kudryavy Volcano, Iturup Island, Kuril Islands, Russia

Field-hunting tip

Look in fumarole deposits country — that is the host setting where rheniite typically forms. If you start seeing molybdenite, pyrite, sulfur in float, you are in the right ground. Field specimens usually show a platy crystals, scales, or massive aggregates habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify rheniite?+

Mohs hardness is 1.5-2. It typically shows a metallic luster. The streak is black. Common colors include black, gray.

Where is rheniite found?+

Notable localities include Kudryavy Volcano, Iturup Island, Kuril Islands, Russia.

How much is rheniite worth?+

Typical asking prices fall in the range of $100-500+ per specimen. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like rheniite?+

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

What minerals are found with rheniite?+

Rheniite commonly co-occurs with Molybdenite, Pyrite, Sulfur. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does rheniite form in?+

Rheniite typically forms in fumarole deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is rheniite used for?+

Rheniite is used in collector, research.

Find rheniite on the map

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