Itoigawaite is a rare strontium-rich member of the lawsonite group, first discovered in the jade-bearing regions of Japan. It typically occurs as fine-grained, translucent green aggregates associated with jadeite deposits in serpentinite environments.

Hardness

6-6.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineralrareLawsonite Group family

Itoigawaite

Hardness: 6-6.5
Luster: Vitreous
Streak: White
Transparency: Translucent

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Is this itoigawaite?

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 itoigawaite with a known reference. Itoigawaite sits at Mohs 6-6.5 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Itoigawaite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Itoigawaite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: green, pale green, yellowish-green.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: fine-grained aggregates, massive.

Often confused with

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

mineral

Jadeite

Mohs 6.5-7

How to tell apart: Luster reads vitreous on Itoigawaite and vitreous to pearly on Jadeite.

How to tell apart: Lawsonite is the harder of the two (Mohs 8 vs. 6-6.5).

Often found alongside itoigawaite

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

All properties

Chemical formula: SrAl₂Si₂O₇(OH)₂·H₂O
Mohs hardness: 6-6.5
Density: 3.37 g/cm³
Colors: Green Pale Green Yellowish-green
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Orthorhombic
Crystal habit: Fine-grained Aggregates, Massive
Cleavage: Distinct
Rarity: Rare
Uses: Collector, Lapidary
Host rock: Serpentinite
Typical price: $50-500 depending on specimen size and quality

Where rockhounds find itoigawaite

Classic worldwide localities

Itoigawa (Niigata Prefecture, Japan)

Field-hunting tip

Look in serpentinite country — that is the host setting where itoigawaite typically forms. If you start seeing jadeite, albite, muscovite in float, you are in the right ground. Field specimens usually show a fine-grained aggregates, massive habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify itoigawaite?+

Mohs hardness is 6-6.5. It typically shows a vitreous luster. The streak is white. Common colors include green, pale green, yellowish-green.

Where is itoigawaite found?+

Notable localities include Itoigawa (Niigata Prefecture, Japan).

How much is itoigawaite 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 itoigawaite?+

Itoigawaite is most often confused with Jadeite, Lawsonite, Prehnite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with itoigawaite?+

Itoigawaite commonly co-occurs with jadeite, albite, muscovite, quartz. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does itoigawaite form in?+

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

What is itoigawaite used for?+

Itoigawaite is used in collector, lapidary.

Find itoigawaite on the map

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