Tocornalite is a rare silver-mercury iodide mineral found in the oxidation zones of silver-rich mineral deposits. It typically occurs as massive, dull-yellow, earthy crusts or coatings on other silver halides and is highly sought after by advanced collectors of rare silver minerals.

Hardness

2-3

Mohs

Luster

Resinous

Streak

Yellow

Transparency

Opaque

mineralrareIodargyrite Group family

Tocornalite

Hardness: 2-3
Luster: Resinous
Streak: Yellow
Transparency: Opaque

Is this tocornalite?

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 tocornalite with a known reference. Tocornalite sits at Mohs 2-3 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Tocornalite leaves a yellow streak.
3
Read the luster
Hold the specimen under a strong light. Tocornalite typically shows a resinous luster.
4
Match the color range
Compare against the expected color range: yellow, pale yellow, brownish yellow.
5
Look at form & habit
Crystal system: hexagonal. Typical habit: massive, crusts, coatings.

Often confused with

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

How to tell apart: Streak differs — Tocornalite leaves yellow, Miargyrite leaves cherry-red; luster reads resinous on Tocornalite and metallic to submetallic on Miargyrite.

Compare →

Often found alongside tocornalite

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

All properties

Chemical formula: (Ag,Hg)I
Mohs hardness: 2-3
Density: 5.7-5.9 g/cm³
Colors: Yellow Pale Yellow Brownish Yellow
Streak: Yellow
Luster: Resinous
Transparency: Opaque
Crystal system: Hexagonal
Crystal habit: Massive, Crusts, Coatings
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Oxidized Zones of Silver Deposits
Typical price: $50-300 per specimen depending on size and provenance

Where rockhounds find tocornalite

Classic worldwide localities

Chañarcillo, Chile
Broken Hill, Australia

Field-hunting tip

Look in oxidized zones of silver deposits country — that is the host setting where tocornalite typically forms. If you start seeing iodargyrite, cerargyrite, native silver in float, you are in the right ground. Field specimens usually show a massive, crusts, coatings habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify tocornalite?+

Mohs hardness is 2-3. It typically shows a resinous luster. The streak is yellow. Common colors include yellow, pale yellow, brownish yellow.

Where is tocornalite found?+

Notable localities include Chañarcillo, Chile; Broken Hill, Australia.

How much is tocornalite worth?+

Typical asking prices fall in the range of $50-300 per specimen depending on size and provenance. Quality, size, and provenance can move individual specimens well outside that range.

Is tocornalite safe to handle?+

It contains toxic constituents. Contains mercury and silver; wash hands thoroughly after handling and avoid inhaling dust or ingesting particles. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like tocornalite?+

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

What minerals are found with tocornalite?+

Tocornalite commonly co-occurs with Iodargyrite, Cerargyrite, Native Silver. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does tocornalite form in?+

Tocornalite typically forms in oxidized zones of silver deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is tocornalite used for?+

Tocornalite is used in collector.

Find tocornalite on the map

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