Shirozulite is a rare manganese-dominant member of the mica group. It is typically found as small, brownish, platy crystals in manganese deposits, often appearing very similar to common biotite mica.

Hardness

Mohs

Streak

White

Transparency

Translucent

mineralrareMica Group family

Shirozulite

Shirozulite is a rare manganese-dominant member of the mica group. It is typically found as small, brownish, platy crystals in manganese deposits, often appearing very similar to common biotite mica.

Hardness: ~3
Streak: White
Transparency: Translucent

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Is this shirozulite?

4-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 shirozulite with a known reference. Shirozulite sits at Mohs ~3, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: white.
3
Match the color range
Compare against the expected color range: dark reddish brown.
4
Look at form & habit
Crystal system: monoclinic. Typical habit: micaceous.

Often confused with

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

How to tell apart: Streak differs, so Shirozulite leaves white, Annite leaves brownish white.

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Often found alongside shirozulite

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

All properties

Chemical formula: KMn₃(Si₃Al)O₁₀(OH)₂
Mohs hardness: ~3
Density: 3.20 g/cm³
Colors: Dark reddish brown
Streak: White
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Micaceous
Cleavage: Perfect on {001}
Rarity: Rare
Uses: Collector
Host rock: In a strata-bound Mn ore deposit formed during regional low-P/T and contact metamorphism

Where rockhounds find shirozulite

Classic worldwide localities

Taguchi mine, Yatuhashi, Kita-shitara County, Aichi Prefecture, Japan

Field-hunting tip

Where it forms: In a strata-bound Mn ore deposit formed during regional low-P/T and contact metamorphism. If you start seeing tephroite, rhodochrosite, apatite in float, you are in the right ground. Typical habit: micaceous. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify shirozulite?+

Mohs hardness is ~3. The streak is white. Common colors include dark reddish brown.

Where is shirozulite found?+

Notable localities include Taguchi mine, Yatuhashi, Kita-shitara County, Aichi Prefecture, Japan.

What rocks look like shirozulite?+

Shirozulite is most often confused with Biotite, Phlogopite, Annite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with shirozulite?+

Shirozulite commonly co-occurs with Tephroite, Rhodochrosite, Apatite, Baryte, Bementite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does shirozulite form in?+

Where it forms: In a strata-bound Mn ore deposit formed during regional low-P/T and contact metamorphism. Working float back to the host body is the standard way to chase a fresh occurrence.

What is shirozulite used for?+

Shirozulite is used in collector.

Find shirozulite on the map

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