Despujolsite is a very rare hydrated calcium strontium sulfate mineral primarily known from fumarolic environments. It typically forms clear, prismatic, hexagonal crystals that are often associated with other sulfate minerals like ettringite. Because of its scarcity, it is sought after primarily by advanced mineral collectors specializing in rare sulfates.

Hardness

2.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Despujolsite

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

Is this despujolsite?

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

Often confused with

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

Often found alongside despujolsite

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

All properties

Chemical formula: Ca₃Sr(SO₄)₂(OH)₄·4H₂O
Mohs hardness: 2.5
Density: 2.75 g/cm³
Colors: Colorless White Yellow
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Hexagonal
Crystal habit: Prismatic Crystals
Cleavage: Perfect Basal
Rarity: Rare
Uses: Collector
Host rock: Fumarolic Deposits
Typical price: $50-300 per specimen

Where rockhounds find despujolsite

Classic worldwide localities

Cerro Pintado, Argentina

Field-hunting tip

Look in fumarolic deposits country — that is the host setting where despujolsite typically forms. If you start seeing gypsum, ettringite, anhydrite in float, you are in the right ground. Field specimens usually show a prismatic crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify despujolsite?+

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

Where is despujolsite found?+

Notable localities include Cerro Pintado, Argentina.

How much is despujolsite 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 despujolsite?+

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

What minerals are found with despujolsite?+

Despujolsite commonly co-occurs with Gypsum, Ettringite, Anhydrite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does despujolsite form in?+

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

What is despujolsite used for?+

Despujolsite is used in collector.

Find despujolsite on the map

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