Smithite is a rare silver arsenic sulfosalt known for its brilliant red color and high refractive index. It typically occurs as small, tabular crystals within the cavities of dolomitic marbles, most famously in the Binnental region of Switzerland. Due to its softness and arsenic content, it is primarily a prize for advanced mineral collectors.

Hardness

1.5-2

Mohs

Luster

Adamantine

Streak

Vermilion

Transparency

Translucent

mineralrare

Smithite

Hardness: 1.5-2
Luster: Adamantine
Streak: Vermilion
Transparency: Translucent

Is this smithite?

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 smithite with a known reference. Smithite 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. Streak: vermilion.
3
Read the luster
Hold the specimen under a strong light. Luster: adamantine.
4
Match the color range
Compare against the expected color range: brown orange, light red, orange red.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: pseudo hexagonal, pyramidal.

Often confused with

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

How to tell apart: Streak differs, so Smithite leaves vermilion, Realgar leaves red-orange to red; luster reads adamantine on Smithite and resinous to greasy on Realgar.

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Often found alongside smithite

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

All properties

Chemical formula: AgAsS₂
Mohs hardness: 1.5-2
Density: 4.88 g/cm³
Colors: Brown orange Light red Orange red
Streak: Vermilion
Luster: Adamantine
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Pseudo hexagonal, pyramidal
Cleavage: Perfect on {100}
Rarity: Rare
Uses: Collector
Host rock: Of hydrothermal origin with other Ag–As sulfides

Where rockhounds find smithite

Classic worldwide localities

Lengenbach quarry, Binntal, Valais, Switzerland (type locality)
Jas Roux deposit, 10 km east of Chapelle-en-Valgaudemar, Hautes-Alpes, France
Wiesloch, Black Forest, Germany
Silvermines, Co. Tipperary, Ireland

Field-hunting tip

Where it forms: Of hydrothermal origin with other Ag–As sulfides. If you start seeing sphalerite, pyrite, realgar in float, you are in the right ground. Typical habit: pseudo hexagonal, pyramidal. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify smithite?+

Mohs hardness is 1.5-2. Luster: adamantine. The streak is vermilion. Common colors include brown orange, light red, orange red.

Where is smithite found?+

Notable localities include Lengenbach quarry, Binntal, Valais, Switzerland (type locality); Jas Roux deposit, 10 km east of Chapelle-en-Valgaudemar, Hautes-Alpes, France; Wiesloch, Black Forest, Germany; Silvermines, Co. Tipperary, Ireland.

Is smithite safe to handle?+

Smithite contains arsenic and calls for real care. Contains arsenic, which is toxic; handle with care and wash hands after touching specimens to avoid ingestion or inhalation of dust.

What rocks look like smithite?+

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

What minerals are found with smithite?+

Smithite commonly co-occurs with Sphalerite, Pyrite, Realgar, Orpiment, Hutchinsonite, Sartorite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does smithite form in?+

Where it forms: Of hydrothermal origin with other Ag–As sulfides. Working float back to the host body is the standard way to chase a fresh occurrence.

What is smithite used for?+

Smithite is used in collector.

Find smithite on the map

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