Maruyamaite is a very rare potassium-dominant member of the tourmaline group, formally described from specimens in Japan. It typically occurs as small, pale-yellow prisms in highly evolved granitic pegmatites. Collectors value it as a significant species for advanced systematic mineral collections.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineralrareTourmaline Group family

Maruyamaite

Hardness: 7
Luster: Vitreous
Streak: White
Transparency: Translucent

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Is this maruyamaite?

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 maruyamaite with a known reference. Maruyamaite sits at Mohs 7, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Maruyamaite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Maruyamaite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: pale yellow, yellowish-brown.
5
Look at form & habit
Crystal system: trigonal. Typical habit: prismatic crystals.

Often confused with

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

Often found alongside maruyamaite

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

All properties

Chemical formula: K(MgLi₂Al₆)(Si₆O₁₈)(BO₃)₃(OH)₃F
Mohs hardness: 7
Density: 3.2 g/cm³
Colors: Pale Yellow Yellowish-brown
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Trigonal
Crystal habit: Prismatic Crystals
Cleavage: Indistinct
Rarity: Rare
Uses: Collector
Host rock: Pegmatites
Typical price: $50-500 depending on specimen size and quality

Where rockhounds find maruyamaite

Classic worldwide localities

Kuschiyama, Japan

Field-hunting tip

Look in pegmatites country, the host setting where maruyamaite typically forms. If you start seeing quartz, feldspar, mica in float, you are in the right ground. Field specimens usually show a prismatic crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify maruyamaite?+

Mohs hardness is 7. It typically shows a vitreous luster. The streak is white. Common colors include pale yellow, yellowish-brown.

Where is maruyamaite found?+

Notable localities include Kuschiyama, Japan.

How much is maruyamaite worth?+

Typical asking prices fall in the range of $50-500 depending on specimen size and quality. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like maruyamaite?+

Maruyamaite is most often confused with Elbaite, Schorl, Dravite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with maruyamaite?+

Maruyamaite commonly co-occurs with Quartz, Feldspar, Mica. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does maruyamaite form in?+

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

What is maruyamaite used for?+

Maruyamaite is used in collector.

Find maruyamaite on the map

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