Écrinsite is a rare amphibole-group mineral primarily documented from the alpine metamorphic rocks of the Massif des Écrins in France. Collectors generally find it as small, dark prismatic crystals within hydrothermal veins or metamorphic lenses alongside minerals like epidote and chlorite.

Hardness

5-6

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineralrareTschermakite family

Écrinsite

Hardness: 5-6
Luster: Vitreous
Streak: White
Transparency: Translucent

No image

Is this écrinsite?

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

Often confused with

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

mineral

Hornblende

Mohs 5-6

How to tell apart: Streak differs — Écrinsite leaves white, Hornblende leaves grayish-white.

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

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Often found alongside écrinsite

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

All properties

Chemical formula: Ca₂(Mg₃Al₂)Si₆Al₂O₂₂(OH)₂
Mohs hardness: 5-6
Density: 3.35 g/cm³
Colors: Dark Green Black Brownish-green
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Prismatic Crystals
Cleavage: Perfect in Two Directions
Rarity: Rare
Uses: Collector
Host rock: Metamorphic Rocks
Typical price: $20-100 per specimen

Where rockhounds find écrinsite

Classic worldwide localities

Massif des Écrins, France

Field-hunting tip

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

Common questions

How do you identify écrinsite?+

Mohs hardness is 5-6. It typically shows a vitreous luster. The streak is white. Common colors include dark green, black, brownish-green.

Where is écrinsite found?+

Notable localities include Massif des Écrins, France.

How much is écrinsite worth?+

Typical asking prices fall in the range of $20-100 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like écrinsite?+

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

What minerals are found with écrinsite?+

Écrinsite commonly co-occurs with Epidote, Albite, Chlorite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does écrinsite form in?+

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

What is écrinsite used for?+

Écrinsite is used in collector.

Find écrinsite on the map

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