Sillénite is a rare bismuth silicate mineral typically found in oxidation zones of bismuth-bearing hydrothermal deposits. It is best identified by its high density and adamantine luster, occurring most frequently as small, yellowish cubic crystals.
Is this sillénite?
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 sillénite with a known reference. Sillénite sits at Mohs 1-2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Sillénite leaves a yellow streak.
- 3Read the lusterHold the specimen under a strong light. Sillénite typically shows a adamantine luster.
- 4Match the color rangeCompare against the expected color range: yellow, yellowish-orange, brown.
- 5Look at form & habitCrystal system: cubic. Typical habit: equant crystals, massive.
Often confused with
Sillénite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Bismite is the harder of the two (Mohs 4.5 vs. 1-2); streak differs, so Sillénite leaves yellow, Bismite leaves gray to yellow; luster reads adamantine on Sillénite and subadamantine to dull to earthy on Bismite.
How to tell apart: Bismutite is the harder of the two (Mohs 3 vs. 1-2); streak differs, so Sillénite leaves yellow, Bismutite leaves gray; luster reads adamantine on Sillénite and vitreous to waxy to dull on Bismutite.
Often found alongside sillénite
Minerals reported to co-occur with sillénite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Bi₁₂SiO₂₀
- Mohs hardness
- 1-2
- Density
- 9.16 g/cm³
- Streak
- Yellow
- Luster
- Adamantine
- Transparency
- Translucent
- Crystal system
- Cubic
- Crystal habit
- Equant Crystals, Massive
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector, Research
- Host rock
- Hydrothermal Veins
Where rockhounds find sillénite
Classic worldwide localities
- Durango, Mexico
Field-hunting tip
Look in hydrothermal veins country, the host setting where sillénite typically forms. If you start seeing bismutite, bismite, quartz in float, you are in the right ground. Field specimens usually show a equant crystals, massive habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify sillénite?+
Where is sillénite found?+
Is sillénite safe to handle?+
What rocks look like sillénite?+
What minerals are found with sillénite?+
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Find sillénite on the map
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