Stilleite is a rare zinc selenide mineral that typically occurs as massive or granular inclusions within sulfide ores. It is primarily identified by its metallic luster and dark gray color in settings where other selenide minerals are present.
Is this stilleite?
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 stilleite with a known reference. Stilleite sits at Mohs ~5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: black.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: gray.
- 5Look at form & habitCrystal system: cubic. Typical habit: inclusions, microscopic crystals.
Often confused with
Stilleite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Stilleite is noticeably harder (Mohs ~5 vs. 3.5-4); streak differs, so Stilleite leaves black, Sphalerite leaves pale brown to pale yellow and white; luster reads metallic on Stilleite and resinous to adamantine on Sphalerite.
How to tell apart: Stilleite is noticeably harder (Mohs ~5 vs. 2.5-3); streak differs, so Stilleite leaves black, Clausthalite leaves grayish black.
How to tell apart: Stilleite is noticeably harder (Mohs ~5 vs. 2.5); streak differs, so Stilleite leaves black, Tiemannite leaves nearly black.
Often found alongside stilleite
Minerals reported to co-occur with stilleite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- ZnSe
- Mohs hardness
- ~5
- Density
- 5.42 g/cm³
- Colors
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque to translucent
- Crystal system
- Cubic
- Crystal habit
- Inclusions, microscopic crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Included in linnaeite (Shinkolobwe, Congo); intermixed with other selenides (Santa Brigida mine, Argentina)
Where rockhounds find stilleite
Classic worldwide localities
- Shinkolobwe, Katanga Province, Congo (Shaba Province, Zaire) (type locality)
- Santa Brigida mine, La Rioja Province, Argentina
- Tilkerode, Harz Mountains, Germany
Field-hunting tip
Where it forms: Included in linnaeite (Shinkolobwe, Congo); intermixed with other selenides (Santa Brigida mine, Argentina). If you start seeing pyrite, linnaeite, clausthalite in float, you are in the right ground. Typical habit: inclusions, microscopic crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify stilleite?+
Where is stilleite found?+
Is stilleite safe to handle?+
What rocks look like stilleite?+
What minerals are found with stilleite?+
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What is stilleite used for?+
Find stilleite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
