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.
Is this millsite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch millsite with a known reference. Millsite sits at Mohs 2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Millsite leaves a pale green streak.
- 3Read the lusterHold the specimen under a strong light. Millsite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: pale royal blue.
- 5Look at form & habitCrystal 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: Streak differs, so Millsite leaves pale green, Teineite leaves pale blue.
How to tell apart: Emmonsite is the harder of the two (Mohs 5 vs. 2); streak differs, so Millsite leaves pale green, Emmonsite leaves pale yellow.
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
- Streak
- Pale Green
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Crusts, Aggregates
- Cleavage
- Perfect On {100}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Tellurium-bearing Ore Deposits
Where rockhounds find millsite
Classic worldwide localities
- Gråurdfjellet, Oppdal, Norway
Field-hunting tip
Look in oxidized tellurium-bearing ore deposits country, the host setting where millsite typically forms. If you start seeing tellurite, paratellurite, quetzalcoatlite in float, you are in the right ground. Field specimens usually show a crusts, aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify millsite?+
Where is millsite found?+
Is millsite safe to handle?+
What rocks look like millsite?+
What minerals are found with millsite?+
What kind of rock does millsite form in?+
What is millsite used for?+
Find millsite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
