Takéuchiite is a rare magnesium-manganese borate mineral typically found in metamorphic manganese deposits. It occurs as small, distinct platy crystals, often associated with other manganese minerals like hausmannite and braunite. It is highly sought after by advanced collectors of rare borate species due to its restricted type localities.

Hardness

Mohs

Luster

Metallic

Streak

Brown

Transparency

Opaque

mineralrareorthopinakiolite group family

Takéuchiite

Hardness: ~6
Luster: Metallic
Streak: Brown
Transparency: Opaque

Is this takéuchiite?

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 takéuchiite with a known reference. Takéuchiite sits at Mohs ~6, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: brown.
3
Read the luster
Hold the specimen under a strong light. Luster: metallic.
4
Match the color range
Compare against the expected color range: black.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: platy crystals.

Often confused with

Takéuchiite vs. its common look-alikes, and how to tell them apart in the field.

mineral

Pinakiolite

Mohs 6

How to tell apart: Streak differs, so Takéuchiite leaves brown, Pinakiolite leaves brownish gray.

Often found alongside takéuchiite

Minerals reported to co-occur with takéuchiite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: Mg₂MnO₂BO₃
Mohs hardness: ~6
Density: 3.93 g/cm³
Colors: Black
Streak: Brown
Luster: Metallic
Transparency: Opaque
Crystal system: Orthorhombic
Crystal habit: Platy crystals
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Very rare in museum specimens from a metamorphosed Fe–Mn orebody

Where rockhounds find takéuchiite

Classic worldwide localities

Långban, Värmland, Sweden

Field-hunting tip

Where it forms: Very rare in museum specimens from a metamorphosed Fe–Mn orebody. If you start seeing dolomite, calcite in float, you are in the right ground. Typical habit: platy crystals. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify takéuchiite?+

Mohs hardness is ~6. Luster: metallic. The streak is brown. Common colors include black.

Where is takéuchiite found?+

Notable localities include Långban, Värmland, Sweden.

What rocks look like takéuchiite?+

Takéuchiite is most often confused with Pinakiolite, Orthopinakiolite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with takéuchiite?+

Takéuchiite commonly co-occurs with Dolomite, Calcite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does takéuchiite form in?+

Where it forms: Very rare in museum specimens from a metamorphosed Fe–Mn orebody. Working float back to the host body is the standard way to chase a fresh occurrence.

What is takéuchiite used for?+

Takéuchiite is used in collector.

Find takéuchiite on the map

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