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

No image

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, 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.