Glaucodot is a rare cobalt-iron sulfarsenide that is frequently confused with arsenopyrite and cobaltite due to its similar metallic appearance. It is typically found in hydrothermal veins associated with other cobalt minerals and is notable for its silver-white to tin-white color that may tarnish to a dull gray.

Hardness

Mohs

Luster

Metallic

Streak

Black

Transparency

Opaque

mineralrareArsenopyrite Group family

Glaucodot

Hardness: 5
Luster: Metallic
Streak: Black
Transparency: Opaque

Is this glaucodot?

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 glaucodot with a known reference. Glaucodot sits at Mohs 5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: black.
3
Read the luster
Hold the specimen under a strong light. Luster: metallic.
4
Match the color range
Compare against the expected color range: grayish tin white, reddish silver white.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: massive.

Often confused with

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

How to tell apart: Streak differs, so Glaucodot leaves black, Cobaltite leaves grayish black.

Often found alongside glaucodot

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

All properties

Chemical formula: (Co,Fe)AsS
Mohs hardness: 5
Density: 6.055 g/cm³
Colors: Grayish tin whiteReddish silver white
Streak: Black
Luster: Metallic
Transparency: Opaque
Crystal system: Orthorhombic
Crystal habit: Massive
Cleavage: Perfect on {010}, less so on {101}
Rarity: Rare
Uses: Collector
Host rock: In deep-seated deposits of high-temperature hydrothermal origin

Where rockhounds find glaucodot

Classic worldwide localities

Standard Consolidated mine, Sumpter, Grant Co., Oregon, and at Franconia, Grafton Co., New Hampshire, USA
Huasco, Tarapacá, Chile (type locality)
Cobalt-Gowganda district, Ontario, Canada
Håkansböda, Västmanland, as large twinned and untwinned crystals, Sweden
Tunaberg, Södermanland, Sweden
Skutterud, Norway

Field-hunting tip

Where it forms: In deep-seated deposits of high-temperature hydrothermal origin. If you start seeing cobaltite, pyrite, chalcopyrite in float, you are in the right ground. Typical habit: massive. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify glaucodot?+

Mohs hardness is 5. Luster: metallic. The streak is black. Common colors include grayish tin white, reddish silver white.

Where is glaucodot found?+

Notable localities include Standard Consolidated mine, Sumpter, Grant Co., Oregon, and at Franconia, Grafton Co., New Hampshire, USA; Huasco, Tarapacá, Chile (type locality); Cobalt-Gowganda district, Ontario, Canada; Håkansböda, Västmanland, as large twinned and untwinned crystals, Sweden; Tunaberg, Södermanland, Sweden.

Is glaucodot safe to handle?+

Glaucodot contains arsenic and cobalt and calls for real care. Contains arsenic. Handle with care, wash hands after handling, avoid creating dust, and keep away from children and food preparation areas.

What rocks look like glaucodot?+

Glaucodot is most often confused with Arsenopyrite, Cobaltite, Skutterudite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with glaucodot?+

Glaucodot commonly co-occurs with Cobaltite, Pyrite, Chalcopyrite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does glaucodot form in?+

Where it forms: In deep-seated deposits of high-temperature hydrothermal origin. Working float back to the host body is the standard way to chase a fresh occurrence.

What is glaucodot used for?+

Glaucodot is used in collector.

Find glaucodot on the map

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