Masutomilite is a rare manganese-rich lithium mica that is primarily sought after by advanced collectors of rare pegmatite minerals. It is typically found in small, delicate tabular crystals or platy aggregates, frequently occurring in lithium-bearing granite pegmatites associated with other rare silicate minerals.

Hardness

2.5-3

Mohs

Luster

Pearly

Streak

White

Transparency

Translucent

mineralrareMica Group family

Masutomilite

Hardness: 2.5-3
Luster: Pearly
Streak: White
Transparency: Translucent

Is this masutomilite?

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 masutomilite with a known reference. Masutomilite sits at Mohs 2.5-3 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Masutomilite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Masutomilite typically shows a pearly luster.
4
Match the color range
Compare against the expected color range: pale pink, violet, lilac, yellowish.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: tabular crystals, micaceous flakes.

Often confused with

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

Often found alongside masutomilite

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

All properties

Chemical formula: KLiAlMn(AlSi₃O₁₀)(F,OH)₂
Mohs hardness: 2.5-3
Density: 3.08 g/cm³
Colors: Pale Pink Violet Lilac Yellowish
Streak: White
Luster: Pearly
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Tabular Crystals, Micaceous Flakes
Cleavage: Perfect Basal
Rarity: Rare
Uses: Collector
Host rock: Granite Pegmatites
Typical price: $20-150 per specimen

Where rockhounds find masutomilite

Classic worldwide localities

Tanokami Mountains, Japan
Hagendorf, Germany
Cruzeiro mine, Brazil

Field-hunting tip

Look in granite pegmatites country — that is the host setting where masutomilite typically forms. If you start seeing quartz, albite, topaz in float, you are in the right ground. Field specimens usually show a tabular crystals, micaceous flakes habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify masutomilite?+

Mohs hardness is 2.5-3. It typically shows a pearly luster. The streak is white. Common colors include pale pink, violet, lilac, yellowish.

Where is masutomilite found?+

Notable localities include Tanokami Mountains, Japan; Hagendorf, Germany; Cruzeiro mine, Brazil.

How much is masutomilite worth?+

Typical asking prices fall in the range of $20-150 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like masutomilite?+

Masutomilite is most often confused with Lepidolite, Polylithionite, Muscovite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with masutomilite?+

Masutomilite commonly co-occurs with Quartz, Albite, Topaz, Cassiterite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does masutomilite form in?+

Masutomilite typically forms in granite pegmatites. Working float back to the host body is the standard way to chase a fresh occurrence.

What is masutomilite used for?+

Masutomilite is used in collector.

Find masutomilite on the map

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