Cesiodymite is a rare cesium potassium copper sulfate. It was approved as a distinct mineral species in 2016. It was first described from Arsenatnaya fumarole, Second scoria cone, Tolbachik volcano, Kamchatka Peninsula, Russia.
Is this cesiodymite?
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 cesiodymite with a known reference. Cesiodymite sits at Mohs 2.5-3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Cesiodymite leaves a pale green streak.
- 3Read the lusterHold the specimen under a strong light. Cesiodymite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: light green, green.
- 5Look at form & habitCrystal system: triclinic. Typical habit: platy crystals.
Often confused with
Cesiodymite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Cesiodymite leaves pale green, Phlogopite leaves white; luster reads vitreous on Cesiodymite and pearly on Phlogopite.
How to tell apart: Streak differs, so Cesiodymite leaves pale green, Muscovite leaves white; luster reads vitreous on Cesiodymite and pearly on Muscovite.
Often found alongside cesiodymite
Minerals reported to co-occur with cesiodymite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CsKCu₅O(SO₄)₅
- Mohs hardness
- 2.5-3
- Density
- 3.593 g/cm³
- Colors
- Streak
- Pale Green
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Triclinic
- Crystal habit
- Platy Crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Granite Pegmatites
Where rockhounds find cesiodymite
Classic worldwide localities
- Kola Peninsula, Russia
Field-hunting tip
Look in granite pegmatites country, the host setting where cesiodymite typically forms. If you start seeing microcline, quartz, albite in float, you are in the right ground. Field specimens usually show a platy crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify cesiodymite?+
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Find cesiodymite on the map
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