Iltisite is an extremely rare mercury halide mineral typically found as small, vibrant yellow platy crystals. It is primarily known from its type locality in Austria, where it occurs as a secondary mineral in association with other mercury species. Collectors prize it for its scarcity and distinct crystalline appearance within mercury-rich mineral assemblages.

Hardness

Mohs

Luster

Adamantine

Streak

Yellow

Transparency

Translucent

mineralrare

Iltisite

Hardness: 2
Luster: Adamantine
Streak: Yellow
Transparency: Translucent

No image

Is this iltisite?

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 iltisite with a known reference. Iltisite sits at Mohs 2 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Iltisite leaves a yellow streak.
3
Read the luster
Hold the specimen under a strong light. Iltisite typically shows a adamantine luster.
4
Match the color range
Compare against the expected color range: yellow, orange-yellow.
5
Look at form & habit
Crystal system: trigonal. Typical habit: platy crystals, granular aggregates.

Often confused with

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

mineral

Calomel

Mohs 1.5-2

How to tell apart: Streak differs — Iltisite leaves yellow, Calomel leaves white.

Often found alongside iltisite

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

All properties

Chemical formula: Hg₂S(Cl,Br)₂
Mohs hardness: 2
Density: 6.8 g/cm³
Colors: Yellow Orange-yellow
Streak: Yellow
Luster: Adamantine
Transparency: Translucent
Crystal system: Trigonal
Crystal habit: Platy Crystals, Granular Aggregates
Cleavage: Perfect On {0001}
Rarity: Rare
Uses: Collector
Host rock: Hydrothermal Veins in Limestone
Typical price: $100-500 thumbnail

Where rockhounds find iltisite

Classic worldwide localities

Iltis Valley, near Kalsdorf, Austria

Field-hunting tip

Look in hydrothermal veins in limestone country — that is the host setting where iltisite typically forms. If you start seeing cinnabar, calomel, terlinguaite in float, you are in the right ground. Field specimens usually show a platy crystals, granular aggregates habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify iltisite?+

Mohs hardness is 2. It typically shows a adamantine luster. The streak is yellow. Common colors include yellow, orange-yellow.

Where is iltisite found?+

Notable localities include Iltis Valley, near Kalsdorf, Austria.

How much is iltisite worth?+

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

Is iltisite safe to handle?+

It contains toxic constituents. Contains mercury; handle with caution, avoid ingestion, inhalation of dust, or prolonged skin contact, and wash hands thoroughly after handling. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like iltisite?+

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

What minerals are found with iltisite?+

Iltisite commonly co-occurs with cinnabar, calomel, terlinguaite, eglestonite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does iltisite form in?+

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

What is iltisite used for?+

Iltisite is used in collector.

Find iltisite on the map

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