Yagiite is a rare sodium-rich member of the osumilite group, typically found as small, clear, hexagonal prismatic crystals within basaltic rocks. It is chemically distinct due to its high sodium content and is primarily a scientific rarity for mineral collectors. It is most famous for its occurrence in the Kogachi basalt in Okinawa, Japan.

Hardness

6-7

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrareOsumilite Group family

Yagiite

Hardness: 6-7
Luster: Vitreous
Streak: White
Transparency: Transparent

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Is this yagiite?

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 yagiite with a known reference. Yagiite sits at Mohs 6-7 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Yagiite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Yagiite 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: hexagonal prismatic crystals.

Often confused with

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

Often found alongside yagiite

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

All properties

Chemical formula: (Na,K)₃Mg₂(Al₃Si₁₂)O₃₀
Mohs hardness: 6-7
Density: 2.66 g/cm³
Colors: Colorless White
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Hexagonal
Crystal habit: Hexagonal Prismatic Crystals
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Alkali Basalts
Typical price: $50-300 per specimen

Where rockhounds find yagiite

Classic worldwide localities

Kogachi, Okinawa Prefecture, Japan

Field-hunting tip

Look in alkali basalts country — that is the host setting where yagiite typically forms. If you start seeing nepheline, augite, apatite in float, you are in the right ground. Field specimens usually show a hexagonal prismatic crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify yagiite?+

Mohs hardness is 6-7. It typically shows a vitreous luster. The streak is white. Common colors include colorless, white.

Where is yagiite found?+

Notable localities include Kogachi, Okinawa Prefecture, Japan.

How much is yagiite worth?+

Typical asking prices fall in the range of $50-300 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like yagiite?+

Yagiite is most often confused with Osumilite, Cordierite, Beryl. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with yagiite?+

Yagiite commonly co-occurs with Nepheline, Augite, Apatite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does yagiite form in?+

Yagiite typically forms in alkali basalts. Working float back to the host body is the standard way to chase a fresh occurrence.

What is yagiite used for?+

Yagiite is used in collector.

Find yagiite on the map

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