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.

Hardness

Mohs

Luster

Submetallic

Streak

Black

Transparency

Opaque

mineralrareLudwigite Group family

Vonsenite

Hardness: 5
Luster: Submetallic
Streak: Black
Transparency: Opaque

Is this vonsenite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch vonsenite with a known reference. Vonsenite sits at Mohs 5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Vonsenite leaves a black streak.
3
Read the luster
Hold the specimen under a strong light. Vonsenite typically shows a submetallic luster.
4
Match the color range
Compare against the expected color range: black.
5
Look at form & habit
Crystal 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.

How to tell apart: Luster reads submetallic on Vonsenite and metallic on Magnetite.

Compare →

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: Black
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, 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

How do you identify vonsenite?+

Mohs hardness is 5. It typically shows a submetallic luster. The streak is black. Common colors include black.

Where is vonsenite found?+

Notable localities include Riverside County, California, USA; Brooks Mountain, Alaska, USA; Dognecea, Romania; Sayama, Japan.

How much is vonsenite worth?+

Typical asking prices fall in the range of $20-150 for thumbnail to small cabinet specimens. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like vonsenite?+

Vonsenite is most often confused with Ludwigite, Ilvaite, Magnetite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with vonsenite?+

Vonsenite commonly co-occurs with Calcite, Magnetite, Forsterite, Ludwigite, Diopside. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does vonsenite form in?+

Vonsenite typically forms in contact metamorphic zones in limestone. Working float back to the host body is the standard way to chase a fresh occurrence.

What is vonsenite used for?+

Vonsenite is used in collector, research.

Find vonsenite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.