Vonsenite is a rare iron-rich borate mineral typically found as black, acicular, or prismatic crystals within contact metamorphic zones. It is often distinguished from similar iron minerals by its occurrence in specific boron-bearing skarns and its submetallic luster.
Is this vonsenite?
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 vonsenite with a known reference. Vonsenite 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. Vonsenite leaves a black streak.
- 3Read the lusterHold the specimen under a strong light. Vonsenite typically shows a submetallic luster.
- 4Match the color rangeCompare against the expected color range: black.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: acicular or prismatic crystals, commonly in radiating aggregates or massive forms.
Often confused with
Vonsenite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside vonsenite
Minerals reported to co-occur with vonsenite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe₂²⁺Fe³⁺BO₅
- Mohs hardness
- 5
- Density
- 4.5-4.8 g/cm³
- Colors
- Streak
- Black
- Luster
- Submetallic
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Acicular or Prismatic Crystals, Commonly in Radiating Aggregates or Massive Forms
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector, Research
- Host rock
- Contact Metamorphic Zones in Limestone
- Typical price
- $20-150 for thumbnail to small cabinet specimens
Where rockhounds find vonsenite
Classic worldwide localities
- Riverside County, California, USA
- Brooks Mountain, Alaska, USA
- Dognecea, Romania
- Sayama, Japan
Field-hunting tip
Look in contact metamorphic zones in limestone country — that is the host setting where vonsenite typically forms. If you start seeing calcite, magnetite, forsterite in float, you are in the right ground. Field specimens usually show a acicular or prismatic crystals, commonly in radiating aggregates or massive forms habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find vonsenite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
