Pyrosmalite-(Mn) is a rare phyllosilicate known for its distinct hexagonal, pearly-lustered plates. It is typically found in contact-metamorphosed manganese-rich ore bodies and is highly valued by mineral collectors for its unique crystal structure and localized occurrences.

Hardness

4-4.5

Mohs

Luster

Pearly on {0001}

Streak

Brownish yellow

Transparency

Translucent

mineralrarePyrosmalite Group family

Pyrosmalite-(Mn)

Hardness: 4-4.5
Luster: Pearly on {0001}
Streak: Brownish yellow
Transparency: Translucent

Is this pyrosmalite-(mn)?

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 pyrosmalite-(mn) with a known reference. Pyrosmalite-(Mn) sits at Mohs 4-4.5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: brownish yellow.
3
Read the luster
Hold the specimen under a strong light. Luster: pearly on {0001}.
4
Match the color range
Compare against the expected color range: green blackish, pale liver brown, gray.
5
Look at form & habit
Crystal system: trigonal. Typical habit: massive, prismatic.

Often confused with

Pyrosmalite-(Mn) vs. its common look-alikes, and how to tell them apart in the field.

mineral

Stilpnomelane

Mohs 3-4

How to tell apart: Streak differs, so Pyrosmalite-(Mn) leaves brownish yellow, Stilpnomelane leaves gray white.

How to tell apart: Pyrosmalite-(Mn) is noticeably harder (Mohs 4-4.5 vs. 2.5-3); streak differs, so Pyrosmalite-(Mn) leaves brownish yellow, Biotite leaves white; luster reads pearly on {0001} on Pyrosmalite-(Mn) and splendent to submetallic, vitreous, pearly on cleavage on Biotite.

How to tell apart: Pyrosmalite-(Mn) is noticeably harder (Mohs 4-4.5 vs. 2-3); streak differs, so Pyrosmalite-(Mn) leaves brownish yellow, Phlogopite leaves white.

Compare →

Often found alongside pyrosmalite-(mn)

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

All properties

Chemical formula: Mn₈Si₆O₁₅(OH,Cl)₁₀
Mohs hardness: 4-4.5
Density: 3.06-3.19 g/cm³
Colors: Green blackishPale liver brownGray
Streak: Brownish yellow
Luster: Pearly on {0001}
Transparency: Translucent
Crystal system: Trigonal
Crystal habit: Massive, prismatic
Cleavage: Perfect on {0001}, {1010} less perfect
Rarity: Rare
Uses: Collector
Host rock: As veinlets in the franklinite ore of a metamorphosed stratiform zinc deposit (Sterling Hill, New Jersey, USA)

Where rockhounds find pyrosmalite-(mn)

Classic worldwide localities

Sterling Hill, Ogdensburg, Sussex Co., New Jersey, USA
Kyurazawa mine, Ashio, Tochigi Prefecture, Japan
Broken Hill, New South Wales, Australia
Pyrosmalite series minerals (with Mn:Fe around one) occur at: Nordmark, Värmland, and Dannemora, Kopparberg, Sweden
Takanosu mine, Takarazawa, Tochigi Prefecture, Japan
Nant Fracon, Wales

Field-hunting tip

Where it forms: As veinlets in the franklinite ore of a metamorphosed stratiform zinc deposit (Sterling Hill, New Jersey, USA). If you start seeing friedelite, bementite, willemite in float, you are in the right ground. Typical habit: massive, prismatic. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify pyrosmalite-(mn)?+

Mohs hardness is 4-4.5. Luster: pearly on {0001}. The streak is brownish yellow. Common colors include green blackish, pale liver brown, gray.

Where is pyrosmalite-(mn) found?+

Notable localities include Sterling Hill, Ogdensburg, Sussex Co., New Jersey, USA; Kyurazawa mine, Ashio, Tochigi Prefecture, Japan; Broken Hill, New South Wales, Australia; Pyrosmalite series minerals (with Mn:Fe around one) occur at: Nordmark, Värmland, and Dannemora, Kopparberg, Sweden; Takanosu mine, Takarazawa, Tochigi Prefecture, Japan.

Is pyrosmalite-(mn) safe to handle?+

Contains manganese and chlorine; wash hands thoroughly after handling to prevent ingestion of dust or trace particles.

What rocks look like pyrosmalite-(mn)?+

Pyrosmalite-(Mn) is most often confused with Stilpnomelane, Biotite, Phlogopite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with pyrosmalite-(mn)?+

Pyrosmalite-(Mn) commonly co-occurs with Friedelite, Bementite, Willemite, Spessartine, Manganoan tremolite, Quartz. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does pyrosmalite-(mn) form in?+

Where it forms: As veinlets in the franklinite ore of a metamorphosed stratiform zinc deposit (Sterling Hill, New Jersey, USA). Working float back to the host body is the standard way to chase a fresh occurrence.

What is pyrosmalite-(mn) used for?+

Pyrosmalite-(Mn) is used in collector.

Find pyrosmalite-(mn) on the map

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