Nestolaite is a rare calcium sulfate hemihydrate found in volcanic fumaroles. It typically occurs as small tabular crystals or crusts associated with other secondary minerals around active volcanic vents.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Nestolaite

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

Is this nestolaite?

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

Often confused with

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

How to tell apart: Bassanite is the harder of the two (Mohs 3 vs. 2).

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Often found alongside nestolaite

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

Gypsum
mineral · Mohs 2

All properties

Chemical formula: CaSO₄·0.5H₂O
Mohs hardness: 2
Density: 2.44 g/cm³
Colors: White Colorless
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Triclinic
Crystal habit: Tabular Crystals, Granular Aggregates
Cleavage: Perfect in One Direction
Rarity: Rare
Uses: Collector
Host rock: Fumarolic Deposits
Typical price: $20-100 per specimen

Where rockhounds find nestolaite

Classic worldwide localities

La Fossa crater, Vulcano, Aeolian Islands, Italy

Field-hunting tip

Look in fumarolic deposits country — that is the host setting where nestolaite typically forms. If you start seeing gypsum, alum-group minerals, sulphur in float, you are in the right ground. Field specimens usually show a tabular crystals, granular aggregates habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify nestolaite?+

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

Where is nestolaite found?+

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

How much is nestolaite worth?+

Typical asking prices fall in the range of $20-100 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like nestolaite?+

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

What minerals are found with nestolaite?+

Nestolaite commonly co-occurs with Gypsum, Alum-group minerals, Sulphur. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does nestolaite form in?+

Nestolaite typically forms in fumarolic deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is nestolaite used for?+

Nestolaite is used in collector.

Find nestolaite on the map

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