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 ~3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: pale green.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: 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 to submetallic on cleavage on Phlogopite.
How to tell apart: Streak differs, so Cesiodymite leaves pale green, Muscovite leaves white.
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
- ~3
- Density
- 3.593 g/cm³
- Colors
- Streak
- Pale green
- Luster
- Vitreous
- Transparency
- Transparent to translucent
- Crystal system
- Triclinic
- Crystal habit
- Platy crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- As sublimates on basaltic scoria near a volcanic fumarole (>350-400 °C.)
Where rockhounds find cesiodymite
Classic worldwide localities
- Arsenatnaya fumarole, Second scoria cone, Tolbachik volcano, Kamchatka Peninsula, Russia
Field-hunting tip
Where it forms: As sublimates on basaltic scoria near a volcanic fumarole (>350-400 °C.). If you start seeing cryptochalcite, euchlorine, chalcocyanite in float, you are in the right ground. Typical habit: platy crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify cesiodymite?+
Where is cesiodymite found?+
Is cesiodymite safe to handle?+
What rocks look like cesiodymite?+
What minerals are found with cesiodymite?+
What kind of rock does cesiodymite form in?+
What is cesiodymite used for?+
Find cesiodymite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
