Avogadrite is a rare potassium fluoroborate mineral primarily found as a sublimation product in volcanic fumaroles. It typically occurs as tiny, colorless to white tabular crystals or crusts, often associated with other rare volcanic halides.

Hardness

2.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Avogadrite

Hardness: 2.5
Luster: Vitreous
Streak: White
Transparency: Transparent

Is this avogadrite?

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 avogadrite with a known reference. Avogadrite sits at Mohs 2.5 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Avogadrite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Avogadrite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: colorless, white.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: tabular crystals, incrustations, granular aggregates.

Often confused with

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

Often found alongside avogadrite

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

All properties

Chemical formula: (K,Cs)BF₄
Mohs hardness: 2.5
Density: 2.62 g/cm³
Colors: Colorless White
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Orthorhombic
Crystal habit: Tabular Crystals, Incrustations, Granular Aggregates
Cleavage: Poor
Rarity: Rare
Uses: Collector
Host rock: Fumaroles in Volcanic Environments
Typical price: $50-300 per specimen depending on size and quality

Where rockhounds find avogadrite

Classic worldwide localities

Mount Vesuvius, Italy
Vulcano, Lipari Islands, Italy
Kamchatka Peninsula, Russia

Field-hunting tip

Look in fumaroles in volcanic environments country — that is the host setting where avogadrite typically forms. If you start seeing malladrite, hieratite, sulphur in float, you are in the right ground. Field specimens usually show a tabular crystals, incrustations, granular aggregates habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify avogadrite?+

Mohs hardness is 2.5. It typically shows a vitreous luster. The streak is white. Common colors include colorless, white.

Where is avogadrite found?+

Notable localities include Mount Vesuvius, Italy; Vulcano, Lipari Islands, Italy; Kamchatka Peninsula, Russia.

How much is avogadrite worth?+

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

Is avogadrite safe to handle?+

It contains toxic constituents. Contains boron and fluorine; handle with care to avoid inhalation of dust or ingestion. Wash hands thoroughly after handling. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like avogadrite?+

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

What minerals are found with avogadrite?+

Avogadrite commonly co-occurs with Malladrite, Hieratite, Sulphur. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does avogadrite form in?+

Avogadrite typically forms in fumaroles in volcanic environments. Working float back to the host body is the standard way to chase a fresh occurrence.

What is avogadrite used for?+

Avogadrite is used in collector.

Find avogadrite on the map

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