Cobaltkoritnigite is a rare cobalt-bearing arsenate mineral typically found as small, delicate, rose-pink bladed crystals or crusts. It is most frequently encountered in the oxidation zones of cobalt-rich hydrothermal veins where it forms in association with other secondary arsenates.

Hardness

2-3

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrareKoritnigite Group family

Cobaltkoritnigite

Hardness: 2-3
Luster: Vitreous
Streak: White
Transparency: Transparent

Is this cobaltkoritnigite?

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 cobaltkoritnigite with a known reference. Cobaltkoritnigite sits at Mohs 2-3, 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.
4
Match the color range
Compare against the expected color range: dark pink, purple red, purple.
5
Look at form & habit
Crystal system: triclinic. Typical habit: bladed crystals, radial aggregates, crusts.

Often confused with

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

How to tell apart: Luster reads vitreous on Cobaltkoritnigite and pearly on {010} on Koritnigite.

Often found alongside cobaltkoritnigite

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

All properties

Chemical formula: Co(AsO₃OH)·H₂O
Mohs hardness: 2-3
Density: 3.46 g/cm³
Colors: Dark pinkPurple red Purple
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Triclinic
Crystal habit: Bladed crystals, radial aggregates, crusts
Cleavage: {010}, perfect; {100}, good
Rarity: Rare
Uses: Collector
Host rock: A weathering product of glaucodot (Saxony, Germany); altering from cobaltite (Bauhaus district, Germany)

Where rockhounds find cobaltkoritnigite

Classic worldwide localities

Erzgebirge, Saxony, probably from the Schwarzenberg district, and at Frohnau, near Annaberg, Germany
Bauhaus district, Richelsdorf Mountains, Hesse, Germany
Sophia mine, near Wittichen, in the Rötenbach quarry, near Alpirsbach and in the Anton mine, Heubachtal, near Schiltach, Black Forest, Germany
Jáchymov (Joachimsthal), Czech Republic

Field-hunting tip

Where it forms: A weathering product of glaucodot (Saxony, Germany); altering from cobaltite (Bauhaus district, Germany). If you start seeing erythrite–köttigite, sphaerocobaltite, pitticite in float, you are in the right ground. Typical habit: bladed crystals, radial aggregates, crusts. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify cobaltkoritnigite?+

Mohs hardness is 2-3. Luster: vitreous. The streak is white. Common colors include dark pink, purple red, purple.

Where is cobaltkoritnigite found?+

Notable localities include Erzgebirge, Saxony, probably from the Schwarzenberg district, and at Frohnau, near Annaberg, Germany; Bauhaus district, Richelsdorf Mountains, Hesse, Germany; Sophia mine, near Wittichen, in the Rötenbach quarry, near Alpirsbach and in the Anton mine, Heubachtal, near Schiltach, Black Forest, Germany; Jáchymov (Joachimsthal), Czech Republic.

Is cobaltkoritnigite safe to handle?+

Cobaltkoritnigite contains arsenic and cobalt and calls for real care. Contains arsenic. Wash hands thoroughly after handling and avoid inhaling dust or powder.

What rocks look like cobaltkoritnigite?+

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

What minerals are found with cobaltkoritnigite?+

Cobaltkoritnigite commonly co-occurs with Erythrite–köttigite, Sphaerocobaltite, Pitticite, Glaucodot, Löllingite–safflorite, Arsenopyrite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does cobaltkoritnigite form in?+

Where it forms: A weathering product of glaucodot (Saxony, Germany); altering from cobaltite (Bauhaus district, Germany). Working float back to the host body is the standard way to chase a fresh occurrence.

What is cobaltkoritnigite used for?+

Cobaltkoritnigite is used in collector.

Find cobaltkoritnigite on the map

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