Ilvaite is a striking, iron-rich silicate typically found in black, vertically striated prismatic crystals. It is most frequently encountered in contact metamorphic zones known as skarns, where it forms in association with other calc-silicate minerals. Collectors often prize it for the sharp, well-defined crystal habits that can sometimes form large, impressive clusters.
Is this ilvaite?
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 ilvaite with a known reference. Ilvaite sits at Mohs 5.5-6 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Ilvaite leaves a black streak.
- 3Read the lusterHold the specimen under a strong light. Ilvaite typically shows a submetallic luster.
- 4Match the color rangeCompare against the expected color range: black, brownish-black.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: prismatic, striated, columnar.
Often confused with
Ilvaite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Tourmaline is the harder of the two (Mohs 7-7.5 vs. 5.5-6); streak differs — Ilvaite leaves black, Tourmaline leaves white; luster reads submetallic on Ilvaite and vitreous on Tourmaline.
How to tell apart: Streak differs — Ilvaite leaves black, Arfvedsonite leaves grey to bluish-grey; luster reads submetallic on Ilvaite and vitreous on Arfvedsonite.
Often found alongside ilvaite
Minerals reported to co-occur with ilvaite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaFe²⁺₂Fe³⁺(Si₂O₇)O(OH)
- Mohs hardness
- 5.5-6
- Density
- 3.8-4.1 g/cm³
- Colors
- Streak
- Black
- Luster
- Submetallic
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Prismatic, Striated, Columnar
- Cleavage
- Poor
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- Contact Metamorphic Skarns
- Typical price
- $10-100 per specimen
Where rockhounds find ilvaite
Classic worldwide localities
- Elba, Italy
- Seriphos, Greece
- Skarn areas in Norway
- Idaho, USA
- British Columbia, Canada
Field-hunting tip
Look in contact metamorphic skarns country — that is the host setting where ilvaite typically forms. If you start seeing calcite, quartz, garnet in float, you are in the right ground. Field specimens usually show a prismatic, striated, columnar habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find ilvaite on the map
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