Imayoshiite is an extremely rare calcium aluminum borosilicate mineral known primarily from the Fuka Mine in Japan. It typically occurs as small, colorless, prismatic crystals within skarn environments associated with high-temperature contact metamorphism of limestone.

Hardness

3-4

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrarenull family

Imayoshiite

Hardness: 3-4
Luster: Vitreous
Streak: White
Transparency: Transparent

Is this imayoshiite?

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

Often confused with

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

Often found alongside imayoshiite

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

All properties

Chemical formula: Ca₃Al₂B₆Si₆O₂₄(OH)₈
Mohs hardness: 3-4
Density: 2.19 g/cm³
Colors: Colorless White
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Hexagonal
Crystal habit: Prismatic Crystals
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Skarn
Typical price: n/a

Where rockhounds find imayoshiite

Classic worldwide localities

Fuka Mine, Okayama Prefecture, Japan

Field-hunting tip

Look in skarn country — that is the host setting where imayoshiite typically forms. If you start seeing fukalite, spurrite, ettringite 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 imayoshiite?+

Mohs hardness is 3-4. It typically shows a vitreous luster. The streak is white. Common colors include colorless, white.

Where is imayoshiite found?+

Notable localities include Fuka Mine, Okayama Prefecture, Japan.

How much is imayoshiite worth?+

Typical asking prices fall in the range of n/a. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like imayoshiite?+

Imayoshiite is most often confused with Sakhaite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with imayoshiite?+

Imayoshiite commonly co-occurs with fukalite, spurrite, ettringite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does imayoshiite form in?+

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

What is imayoshiite used for?+

Imayoshiite is used in collector.

Find imayoshiite on the map

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