Millsite is a rare copper tellurite, typically cyan to pale royal blue. It was approved as a distinct mineral species in 2015. It was first described from Gråurdfjellet, Oppdal, Norway.

Hardness

Mohs

Luster

Vitreous

Streak

Pale green

Transparency

Transparent to translucent

mineralrare

Millsite

Millsite is a rare copper tellurite, typically cyan to pale royal blue. It was approved as a distinct mineral species in 2015. It was first described from Gråurdfjellet, Oppdal, Norway.

Hardness: 2
Luster: Vitreous
Streak: Pale green
Transparency: Transparent to translucent

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Is this millsite?

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 millsite with a known reference. Millsite sits at Mohs 2, 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 green.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: pale royal blue, cyan.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: crusts, aggregates.

Often confused with

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

How to tell apart: Emmonsite is the harder of the two (Mohs ~5 vs. 2).

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Often found alongside millsite

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

All properties

Chemical formula: CuTeO₃·2H₂O
Mohs hardness: 2
Density: 3.963 g/cm³
Colors: Pale royal blueCyan
Streak: Pale green
Luster: Vitreous
Transparency: Transparent to translucent
Crystal system: Monoclinic
Crystal habit: Crusts, aggregates
Cleavage: Perfect on {100}
Rarity: Rare
Uses: Collector
Host rock: A secondary mineral found within vugs, interstices and along cracks in granular quartz from a single boulder of quartz-rich granite, probably a glacial erratic

Where rockhounds find millsite

Classic worldwide localities

Gråurdfjellet, Oppdal, Norway

Field-hunting tip

Where it forms: A secondary mineral found within vugs, interstices and along cracks in granular quartz from a single boulder of quartz-rich granite, probably a glacial erratic. If you start seeing teineite, malachite, u-rich mcalpineite in float, you are in the right ground. Typical habit: crusts, aggregates. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify millsite?+

Mohs hardness is 2. Luster: vitreous. The streak is pale green. Common colors include pale royal blue, cyan.

Where is millsite found?+

Notable localities include Gråurdfjellet, Oppdal, Norway.

Is millsite safe to handle?+

Millsite contains copper. Contains copper and tellurium, which are toxic if ingested or inhaled as dust. Wash hands thoroughly after handling and avoid creating dust.

What rocks look like millsite?+

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

What minerals are found with millsite?+

Millsite commonly co-occurs with Teineite, Malachite, U-rich mcalpineite, Schmitterite, Goethite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does millsite form in?+

Where it forms: A secondary mineral found within vugs, interstices and along cracks in granular quartz from a single boulder of quartz-rich granite, probably a glacial erratic. Working float back to the host body is the standard way to chase a fresh occurrence.

What is millsite used for?+

Millsite is used in collector.

Find millsite on the map

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