Glaucophane is a primary indicator mineral for high-pressure, low-temperature metamorphic conditions, often found in blueschist facies rocks. It typically forms long, slender prismatic or fibrous crystals with a distinctive blue or blue-grey coloration.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineralcommonAmphibole Group family

Glaucophane

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

Is this glaucophane?

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 glaucophane with a known reference. Glaucophane sits at Mohs 6 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Glaucophane leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Glaucophane typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: blue, blue-gray, lavender, black.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: prismatic crystals, fibrous, massive, granular.

Often confused with

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

mineral

Riebeckite

Mohs 5-6

How to tell apart: Streak differs — Glaucophane leaves white, Riebeckite leaves blue-gray.

How to tell apart: Luster reads vitreous on Glaucophane and vitreous to silky on Actinolite.

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Often found alongside glaucophane

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

All properties

Chemical formula: Na₂(Mg₃Al₂)(Si₈O₂₂)(OH)₂
Mohs hardness: 6
Density: 3.0-3.2 g/cm³
Colors: Blue Blue-gray Lavender Black
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Prismatic Crystals, Fibrous, Massive, Granular
Cleavage: Perfect On {110}
Rarity: Common
Uses: Collector, Geological Indicator
Host rock: Blueschist Metamorphic Rocks
Typical price: $5-50 for small cabinet specimens

Where rockhounds find glaucophane

Classic worldwide localities

Blueschist facies terranes
Island of Syra, Greece
Sonoma County, California, USA
Ile de Groix, France
Piedmont, Italy

Field-hunting tip

Look in blueschist metamorphic rocks country — that is the host setting where glaucophane typically forms. If you start seeing lawsonite, jadeite, epidote in float, you are in the right ground. Field specimens usually show a prismatic crystals, fibrous, massive, granular habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify glaucophane?+

Mohs hardness is 6. It typically shows a vitreous luster. The streak is white. Common colors include blue, blue-gray, lavender, black.

Where is glaucophane found?+

Notable localities include Blueschist facies terranes; Island of Syra, Greece; Sonoma County, California, USA; Ile de Groix, France; Piedmont, Italy.

How much is glaucophane worth?+

Typical asking prices fall in the range of $5-50 for small cabinet specimens. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like glaucophane?+

Glaucophane is most often confused with Riebeckite, Actinolite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with glaucophane?+

Glaucophane commonly co-occurs with Lawsonite, Jadeite, Epidote, Garnet, Muscovite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does glaucophane form in?+

Glaucophane typically forms in blueschist metamorphic rocks. Working float back to the host body is the standard way to chase a fresh occurrence.

What is glaucophane used for?+

Glaucophane is used in collector, geological indicator.

Find glaucophane on the map

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