Chrysothallite is a rare secondary mineral found in high-temperature fumaroles of volcanic systems. It typically occurs as delicate, bright green to yellow-green platy crystals or thin crusts associated with other exotic copper-bearing chlorides and selenites.
Is this chrysothallite?
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 chrysothallite with a known reference. Chrysothallite 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: yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: bright golden-yellow.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: platy crystals, crusts.
Often confused with
Chrysothallite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside chrysothallite
Minerals reported to co-occur with chrysothallite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- K₆Cu₆TlCl₁₇(OH)₄·H₂O
- Mohs hardness
- ~3
- Density
- 2.95 g/cm³
- Colors
- Bright golden-yellow
- Streak
- Yellow
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Tetragonal
- Crystal habit
- Platy crystals, crusts
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Formed by the interactions among high-temperature sublimate minerals, fumarolic gas and atmospheric water vapor at temperatures not higher than 150 °C
Where rockhounds find chrysothallite
Classic worldwide localities
- Glavnaya Tenoritovaya and Pyatno fumaroles, Second scoria cone, Northern Breakthrough of the Great Tolbachik Fissure Eruption, Tolbachik volcano, Kamchatka, Russia
Field-hunting tip
Where it forms: Formed by the interactions among high-temperature sublimate minerals, fumarolic gas and atmospheric water vapor at temperatures not higher than 150 °C. If you start seeing belloite, avdoninite, chlorothionite in float, you are in the right ground. Typical habit: platy crystals, crusts. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify chrysothallite?+
Where is chrysothallite found?+
Is chrysothallite safe to handle?+
What rocks look like chrysothallite?+
What minerals are found with chrysothallite?+
What kind of rock does chrysothallite form in?+
What is chrysothallite used for?+
Find chrysothallite on the map
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