Stergiouite is a rare calcium zinc arsenate that forms white to colorless clusters of stacked, platy crystals. It is a secondary mineral on amorphous films coating the matrix of a galena and sphalerite-bearing vein. It was first described from the Plaka Mine No. 80, Lavrion District Mines, Attikí Prefecture, Greece.

Hardness

3.5

Mohs

Luster

Pearly

Streak

White

Transparency

Translucent

mineralrare

Stergiouite

Hardness: 3.5
Luster: Pearly
Streak: White
Transparency: Translucent

Is this stergiouite?

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 stergiouite with a known reference. Stergiouite sits at Mohs 3.5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Stergiouite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Stergiouite typically shows a pearly luster.
4
Match the color range
Compare against the expected color range: white, colorless.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: clusters of stacked, platy crystals.

Often confused with

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

mineral

Whewellite

Mohs 2.5-3

How to tell apart: Luster reads pearly on Stergiouite and vitreous on Whewellite.

How to tell apart: Luster reads pearly on Stergiouite and vitreous on Weddellite.

Compare →

Often found alongside stergiouite

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

All properties

Chemical formula: CaZn₂(AsO₄)₂·4H₂O
Mohs hardness: 3.5
Density: 3.1 g/cm³
Colors: White Colorless
Streak: White
Luster: Pearly
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Clusters of Stacked, Platy Crystals
Cleavage: Perfect On {100}
Rarity: Rare
Uses: Collector
Host rock: Slag Heaps and Lead-zinc Hydrothermal Deposits

Where rockhounds find stergiouite

Classic worldwide localities

Lavrion District, Greece

Field-hunting tip

Look in slag heaps and lead-zinc hydrothermal deposits country, the host setting where stergiouite typically forms. If you start seeing galena, sphalerite, smithsonite in float, you are in the right ground. Field specimens usually show a clusters of stacked, platy crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify stergiouite?+

Mohs hardness is 3.5. It typically shows a pearly luster. The streak is white. Common colors include white, colorless.

Where is stergiouite found?+

Notable localities include Lavrion District, Greece.

Is stergiouite safe to handle?+

It contains toxic constituents. Contains arsenic, which is toxic if ingested or inhaled as dust. Wash hands thoroughly after handling and avoid creating dust. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like stergiouite?+

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

What minerals are found with stergiouite?+

Stergiouite commonly co-occurs with Galena, Sphalerite, Smithsonite, Aurichalcite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does stergiouite form in?+

Stergiouite typically forms in slag heaps and lead-zinc hydrothermal deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is stergiouite used for?+

Stergiouite is used in collector.

Find stergiouite on the map

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