Indigo Gabbro is a coarse-grained igneous rock, often trade-named 'Mystic Merlinite', primarily sourced from Madagascar. It is characterized by its deep charcoal-to-indigo base color with swirling inclusions of grey and purple, which take a high polish in lapidary work.

Hardness

6-7

Mohs

Luster

Submetallic

Streak

White

Transparency

Opaque

igneouscommon

Indigo Gabbro

Also: Mystic Merlinite

Hardness: 6-7
Luster: Submetallic
Streak: White
Transparency: Opaque

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Is this indigo gabbro?

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 indigo gabbro with a known reference. Indigo Gabbro 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. Indigo Gabbro leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Indigo Gabbro typically shows a submetallic luster.
4
Match the color range
Compare against the expected color range: black, dark purple, gray.
5
Look at form & habit
Typical habit: massive.

Often confused with

Indigo Gabbro vs. its common look-alikes, and how to tell them apart in the field.

igneous

Gabbro

Mohs 6-7

How to tell apart: Luster reads submetallic on Indigo Gabbro and vitreous on Gabbro.

How to tell apart: Luster reads submetallic on Indigo Gabbro and vitreous on Labradorite.

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Often found alongside indigo gabbro

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

All properties

Mohs hardness: 6-7
Density: 2.8-3.1 g/cm³
Colors: Black Dark Purple Gray
Streak: White
Luster: Submetallic
Transparency: Opaque
Crystal habit: Massive
Cleavage: None
Rarity: Common
Uses: Lapidary, Collector, Decorative
Host rock: Plutonic Igneous Rock
Typical price: $5-50 for slabs and spheres

Where rockhounds find indigo gabbro

Classic worldwide localities

Madagascar

Field-hunting tip

Look in plutonic igneous rock country, the host setting where indigo gabbro typically forms. If you start seeing plagioclase, pyroxene, magnetite in float, you are in the right ground. Field specimens usually show a massive habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify indigo gabbro?+

Mohs hardness is 6-7. It typically shows a submetallic luster. The streak is white. Common colors include black, dark purple, gray.

Where is indigo gabbro found?+

Notable localities include Madagascar.

How much is indigo gabbro worth?+

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

What rocks look like indigo gabbro?+

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

What minerals are found with indigo gabbro?+

Indigo Gabbro commonly co-occurs with Plagioclase, Pyroxene, Magnetite, Chlorite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does indigo gabbro form in?+

Indigo Gabbro typically forms in plutonic igneous rock. Working float back to the host body is the standard way to chase a fresh occurrence.

What is indigo gabbro used for?+

Indigo Gabbro is used in lapidary, collector, decorative.

Find indigo gabbro on the map

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