Rauenthalite is a very rare secondary arsenic mineral that typically occurs as delicate, white acicular crystal sprays or coatings in hydrothermal veins. It is named after its primary type locality in the Rauenthal valley of France and is frequently found alongside other secondary arsenic species. Due to its solubility and fragility, it is a specialized collector's mineral that requires careful handling.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Semitransparent

mineralrareHörnesite Group family

Rauenthalite

Hardness: 2
Luster: Vitreous
Streak: White
Transparency: Semitransparent

Is this rauenthalite?

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 rauenthalite with a known reference. Rauenthalite 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. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: colorless, snow white.
5
Look at form & habit
Crystal system: triclinic. Typical habit: acicular crystals, radiating sprays, crusts.

Often confused with

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

mineral

Hörnesite

Mohs 1

How to tell apart: Rauenthalite is noticeably harder (Mohs 2 vs. 1); luster reads vitreous on Rauenthalite and resinous to waxy, pearly on cleavages on Hörnesite.

Often found alongside rauenthalite

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

All properties

Chemical formula: Ca₃(AsO₄)₂·10H₂O
Mohs hardness: 2
Density: 2.36 g/cm³
Colors: Colorless Snow white
Streak: White
Luster: Vitreous
Transparency: Semitransparent
Crystal system: Triclinic
Crystal habit: Acicular crystals, radiating sprays, crusts
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: A post-mine low-temperature reaction product of carbonate gangue with arsenical solutions derived from arsenic (Sainte-Marie-aux-Mines, France)

Where rockhounds find rauenthalite

Classic worldwide localities

Getchell mine, Potosi district, Humboldt Co., Nevada, USA
Gabe-Gottes mine, Sainte-Marie-aux-Mines, Haut-Rhin, and at the Salsigne mine, 15 km north of Carcassone, Aude, France
Svatá Anna uranium deposit, Planá, near Mariánské Lázně (Marienbad), and Jáchymov (Joachimsthal), Czech Republic
Anton mine, Heubachtal, near Schiltach, and from Wittichen, Black Forest, Germany
St. Andreasberg, Harz Mountains, Germany
Bauhaus district, Richelsdorf Mountains, Hesse, Germany

Field-hunting tip

Where it forms: A post-mine low-temperature reaction product of carbonate gangue with arsenical solutions derived from arsenic (Sainte-Marie-aux-Mines, France). If you start seeing phaunouxite, picropharmacolite, pharmacolite in float, you are in the right ground. Typical habit: acicular crystals, radiating sprays, crusts. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify rauenthalite?+

Mohs hardness is 2. Luster: vitreous. The streak is white. Common colors include colorless, snow white.

Where is rauenthalite found?+

Notable localities include Getchell mine, Potosi district, Humboldt Co., Nevada, USA; Gabe-Gottes mine, Sainte-Marie-aux-Mines, Haut-Rhin, and at the Salsigne mine, 15 km north of Carcassone, Aude, France; Svatá Anna uranium deposit, Planá, near Mariánské Lázně (Marienbad), and Jáchymov (Joachimsthal), Czech Republic; Anton mine, Heubachtal, near Schiltach, and from Wittichen, Black Forest, Germany; St. Andreasberg, Harz Mountains, Germany.

Is rauenthalite safe to handle?+

Rauenthalite contains arsenic and calls for real care. Contains arsenic. Handle with care, avoid creating dust, wash hands thoroughly after contact, and keep away from children.

What rocks look like rauenthalite?+

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

What minerals are found with rauenthalite?+

Rauenthalite commonly co-occurs with Phaunouxite, Picropharmacolite, Pharmacolite, Sainfeldite, Ferrarisite, Löllingite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does rauenthalite form in?+

Where it forms: A post-mine low-temperature reaction product of carbonate gangue with arsenical solutions derived from arsenic (Sainte-Marie-aux-Mines, France). Working float back to the host body is the standard way to chase a fresh occurrence.

What is rauenthalite used for?+

Rauenthalite is used in collector.

Find rauenthalite on the map

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