Adranosite is a rare sulfate mineral typically found as small crusts or delicate crystals within volcanic fumarole vents. It is primarily identified by its occurrence at the La Fossa crater on Vulcano, where it precipitates directly from volcanic gases.

Hardness

2-3

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineralrareAlunite Supergroup family

Adranosite

Hardness: 2-3
Luster: Vitreous
Streak: White
Transparency: Translucent

Is this adranosite?

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 adranosite with a known reference. Adranosite 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. Adranosite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Adranosite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: white, yellow.
5
Look at form & habit
Crystal system: tetragonal. Typical habit: tabular crystals.

Often confused with

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

How to tell apart: Streak differs — Adranosite leaves white, Jarosite leaves yellow.

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Often found alongside adranosite

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

Bismutite
mineral · Mohs 3

All properties

Chemical formula: (NH₄)₄NaFe₂ (SO₄)₄Cl(OH)₂
Mohs hardness: 2-3
Density: 2.73 g/cm³
Colors: White Yellow
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Tetragonal
Crystal habit: Tabular Crystals
Cleavage: None Observed
Rarity: Rare
Uses: Collector
Host rock: Fumarolic Encrustations On Volcanic Rock
Typical price: $50-300 per specimen

Where rockhounds find adranosite

Classic worldwide localities

La Fossa crater, Vulcano, Aeolian Islands, Italy

Field-hunting tip

Look in fumarolic encrustations on volcanic rock country — that is the host setting where adranosite typically forms. If you start seeing sulphur, sal-ammoniac, bismutite in float, you are in the right ground. Field specimens usually show a tabular crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify adranosite?+

Mohs hardness is 2-3. It typically shows a vitreous luster. The streak is white. Common colors include white, yellow.

Where is adranosite found?+

Notable localities include La Fossa crater, Vulcano, Aeolian Islands, Italy.

How much is adranosite worth?+

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

What rocks look like adranosite?+

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

What minerals are found with adranosite?+

Adranosite commonly co-occurs with Sulphur, Sal-ammoniac, Bismutite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does adranosite form in?+

Adranosite typically forms in fumarolic encrustations on volcanic rock. Working float back to the host body is the standard way to chase a fresh occurrence.

What is adranosite used for?+

Adranosite is used in collector.

Find adranosite on the map

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