Malladrite is a rare sodium fluorosilicate typically found as a volcanic sublimated mineral in fumaroles. It often occurs as tiny, thin hexagonal plates or white crusts associated with other fluorine-bearing minerals. Because it is water-soluble and chemically unstable in humid environments, specimens should be stored in a dry, airtight container.

Hardness

Mohs

Luster

Vitreous to greasy

Streak

White

Transparency

Semitransparent

mineralrare

Malladrite

Hardness: 3
Luster: Vitreous to greasy
Streak: White
Transparency: Semitransparent

Is this malladrite?

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 malladrite with a known reference. Malladrite sits at Mohs 3, 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 to greasy.
4
Match the color range
Compare against the expected color range: rose, colorless, white.
5
Look at form & habit
Crystal system: trigonal. Typical habit: crystalline, prismatic.

Often confused with

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

Often found alongside malladrite

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

All properties

Chemical formula: Na₂SiF₆
Mohs hardness: 3
Density: 2.755 g/cm³
Colors: Rose Colorless White
Streak: White
Luster: Vitreous to greasy
Transparency: Semitransparent
Crystal system: Trigonal
Crystal habit: Crystalline, prismatic
Cleavage: Perfect
Rarity: Rare
Uses: Collector
Host rock: As a volcanic sublimate

Where rockhounds find malladrite

Classic worldwide localities

Vesuvius, Campania, and on Vulcano, Lipari Islands, Italy

Field-hunting tip

Where it forms: As a volcanic sublimate. If you start seeing avogadrite, hieratite, sal ammoniac in float, you are in the right ground. Typical habit: crystalline, prismatic. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify malladrite?+

Mohs hardness is 3. Luster: vitreous to greasy. The streak is white. Common colors include rose, colorless, white.

Where is malladrite found?+

Notable localities include Vesuvius, Campania, and on Vulcano, Lipari Islands, Italy.

Is malladrite safe to handle?+

Contains fluorine and can release hazardous hydrogen fluoride gas if treated with acids or heated to high temperatures. Handle with care and avoid dust inhalation.

What rocks look like malladrite?+

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

What minerals are found with malladrite?+

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

What kind of rock does malladrite form in?+

Where it forms: As a volcanic sublimate. Working float back to the host body is the standard way to chase a fresh occurrence.

What is malladrite used for?+

Malladrite is used in collector.

Find malladrite on the map

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