Agricolaite is a rare potassium lead carbonate mineral found in oxidized mineral deposits. It typically forms small, clear, tabular crystals in association with other lead-bearing secondary minerals in the Lavrion mines of Greece.

Hardness

Mohs

Luster

Vitreous

Streak

Pale yellow

Transparency

Translucent

mineralrare

Agricolaite

Hardness: ~4
Luster: Vitreous
Streak: Pale yellow
Transparency: Translucent

Is this agricolaite?

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 agricolaite with a known reference. Agricolaite sits at Mohs ~4, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: pale yellow.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: yellow.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: tabular crystals.

Often confused with

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

mineral

Cerussite

Mohs 3-3.5

How to tell apart: Streak differs, so Agricolaite leaves pale yellow, Cerussite leaves white; luster reads vitreous on Agricolaite and adamantine, tending toward vitreous, resinous on Cerussite.

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Often found alongside agricolaite

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

All properties

Chemical formula: K₄(UO₂)(CO₃)₃
Mohs hardness: ~4
Density: 3.531 g/cm³
Colors: Yellow
Streak: Pale yellow
Luster: Vitreous
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Tabular crystals
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: A secondary weathering mineral in vugs of ankerite gangue in gneiss

Where rockhounds find agricolaite

Classic worldwide localities

Giftkiesstollen adit, Jáchymov, southern slopes of the Krušné hory Mts. (Erzgebirge), ~20 km north of Karlovy Vary, NW Bohemia, Czech Republic

Field-hunting tip

Where it forms: A secondary weathering mineral in vugs of ankerite gangue in gneiss. If you start seeing aragonite, brochantite, posnjakite in float, you are in the right ground. Typical habit: tabular crystals. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify agricolaite?+

Mohs hardness is ~4. Luster: vitreous. The streak is pale yellow. Common colors include yellow.

Where is agricolaite found?+

Notable localities include Giftkiesstollen adit, Jáchymov, southern slopes of the Krušné hory Mts. (Erzgebirge), ~20 km north of Karlovy Vary, NW Bohemia, Czech Republic.

Is agricolaite safe to handle?+

Agricolaite contains uranium or thorium and calls for real care. Contains lead, which is toxic if ingested or inhaled as dust. Always wash hands after handling and keep away from food.

What rocks look like agricolaite?+

Agricolaite is most often confused with Cerussite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with agricolaite?+

Agricolaite commonly co-occurs with Aragonite, Brochantite, Posnjakite, Malachite, Rutherfordine, Pseudo-voglite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does agricolaite form in?+

Where it forms: A secondary weathering mineral in vugs of ankerite gangue in gneiss. Working float back to the host body is the standard way to chase a fresh occurrence.

What is agricolaite used for?+

Agricolaite is used in collector.

Find agricolaite on the map

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