Greenockite is a rare cadmium sulfide mineral that frequently appears as bright yellow or orange crusts and coatings on other minerals like sphalerite. It is prized by collectors for its vivid color and strong fluorescence, but it should be handled with extreme care due to its toxic cadmium content.
Is this greenockite?
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 greenockite with a known reference. Greenockite sits at Mohs 3-3.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: yellow-orange to brick-red.
- 3Read the lusterHold the specimen under a strong light. Luster: adamantine to resinous.
- 4Match the color rangeCompare against the expected color range: honey yellow, citron yellow, orange yellow.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: colloform, encrustations, radial.
Often confused with
Greenockite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Greenockite leaves yellow-orange to brick-red, Sphalerite leaves pale brown to pale yellow and white; luster reads adamantine to resinous on Greenockite and resinous to adamantine on Sphalerite.
How to tell apart: Streak differs, so Greenockite leaves yellow-orange to brick-red, Wurtzite leaves brown; luster reads adamantine to resinous on Greenockite and resinous, brilliant submetallic on crystal faces on Wurtzite.
How to tell apart: Greenockite is noticeably harder (Mohs 3-3.5 vs. 1.5-2); streak differs, so Greenockite leaves yellow-orange to brick-red, Orpiment leaves pale lemon-yellow; luster reads adamantine to resinous on Greenockite and resinous, pearly on cleavage surface on Orpiment.
Often found alongside greenockite
Minerals reported to co-occur with greenockite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CdS
- Mohs hardness
- 3-3.5
- Density
- 4.820 g/cm³
- Colors
- Streak
- Yellow-orange to brick-red
- Luster
- Adamantine to resinous
- Transparency
- Opaque
- Crystal system
- Hexagonal
- Crystal habit
- Colloform, encrustations, radial
- Cleavage
- Distinct on {1122}, imperfect on {0001}
- Rarity
- Uncommon
- Uses
- Collector, Ore of cadmium
- Host rock
- As earthy coatings, especially on sphalerite, in which it also occurs as a substituent; also rarely as crystals in cavities in mafic igneous rocks; in high-temerature hydrothermal vein deposits
Where rockhounds find greenockite
2 mapped spotsClassic worldwide localities
- Franklin and Sterling Hill, Ogdensburg, Sussex Co., New Jersey, USA
- Paterson, Passaic Co., New Jersey, USA
- Fanwood quarry, Somerset Co., New Jersey, USA
- Summit quarry, Union Co., New Jersey, USA
- Bishopton, near Glasgow, Renfrewshire (type locality), prehnite, Scotland
- Coatings on sphalerite in the Leadhills-Wanlockhead district, Dumfries, Scotland
Field-hunting tip
Where it forms: As earthy coatings, especially on sphalerite, in which it also occurs as a substituent; also rarely as crystals in cavities in mafic igneous rocks; in high-temerature hydrothermal vein deposits. If you start seeing sphalerite, smithsonite, prehnite in float, you are in the right ground. Typical habit: colloform, encrustations, radial. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Arkansas, Missouri. Start trip planning there.
Common questions
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Find greenockite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
