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, 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.