Ktenasite is a rare secondary copper-zinc sulfate mineral typically found as vibrant blue to blue-green platy crystals or thin crusts. It is most famous from the ancient mining district of Laurion, Greece, where it forms in the oxidation zones of ore bodies alongside other copper-zinc minerals.
Is this ktenasite?
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 ktenasite with a known reference. Ktenasite sits at Mohs 2-2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: light green.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: blue, blue green, green, emerald green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular.
Often confused with
Ktenasite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Ktenasite leaves light green, Devilline leaves pale green.
How to tell apart: Serpierite is the harder of the two (Mohs 3.5-4 vs. 2-2.5); streak differs, so Ktenasite leaves light green, Serpierite leaves greenish white.
Often found alongside ktenasite
Minerals reported to co-occur with ktenasite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Cu,Zn)₅(SO₄)₂(OH)₆·6H₂O
- Mohs hardness
- 2-2.5
- Density
- 2.94-2.97 g/cm³
- Streak
- Light green
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- An uncommon secondary mineral formed by oxidation of chalcopyrite and sphalerite in Cu–Zn hydrothermal mineral deposits and in mine dumps
Where rockhounds find ktenasite
Classic worldwide localities
- Commodore mine, Creede, Mineral Co., and in the Eagle mine, Gilman district, Eagle Co., Colorado, USA
- Lynchburg mine, nine km south of Magdalena, Socorro Co., New Mexico, USA
- Laurium, from the Kamariza mine, and in slag, Greece
- Trentini and Veneziana mine, near Torrebelvicino, Veneto, Italy
- Glomrudskollen zinc mine, and at Skutterud, Modum, Norway
- Drakewalls mine, Gunnislake, Cornwall, England
Field-hunting tip
Where it forms: An uncommon secondary mineral formed by oxidation of chalcopyrite and sphalerite in Cu–Zn hydrothermal mineral deposits and in mine dumps. If you start seeing glaucocerinite, serpierite, smithsonite in float, you are in the right ground. Typical habit: tabular. Train your eye for that shape before scanning the outcrop.
Common questions
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Find ktenasite on the map
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