Ambrinoite is a rare member of the aeschynite group of minerals, typically occurring in complex granite pegmatites. Collectors should look for dark, submetallic prismatic crystals that often exhibit signs of metamictization due to thorium content. It is prized primarily as a rare earth mineral specimen for advanced radioactive mineral collections.

Hardness

5-6

Mohs

Luster

Submetallic

Streak

Light Brown

Transparency

Opaque

mineralrareAeschynite Group family

Ambrinoite

Hardness: 5-6
Luster: Submetallic
Streak: Light Brown
Transparency: Opaque

Is this ambrinoite?

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 ambrinoite with a known reference. Ambrinoite 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. Ambrinoite leaves a light brown streak.
3
Read the luster
Hold the specimen under a strong light. Ambrinoite typically shows a submetallic luster.
4
Match the color range
Compare against the expected color range: black, dark brown.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: prismatic crystals.

Often confused with

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

mineral

Euxenite

Mohs 5.5-6.5

How to tell apart: Streak differs — Ambrinoite leaves light brown, Euxenite leaves yellowish, grayish, or reddish-brown; luster reads submetallic on Ambrinoite and submetallic, resinous, greasy on Euxenite.

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Often found alongside ambrinoite

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

All properties

Chemical formula: (Y,Ca,Fe,Th)(Ti,Nb)₂(O,OH)₆
Mohs hardness: 5-6
Density: 4.9-5.1 g/cm³
Colors: Black Dark Brown
Streak: Light Brown
Luster: Submetallic
Transparency: Opaque
Crystal system: Orthorhombic
Crystal habit: Prismatic Crystals
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Granite Pegmatites
Typical price: $50-300 per specimen

Where rockhounds find ambrinoite

Classic worldwide localities

Hitterø, Norway
Kola Peninsula, Russia

Field-hunting tip

Look in granite pegmatites country — that is the host setting where ambrinoite typically forms. If you start seeing zircon, monazite, feldspar 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 ambrinoite?+

Mohs hardness is 5-6. It typically shows a submetallic luster. The streak is light brown. Common colors include black, dark brown.

Where is ambrinoite found?+

Notable localities include Hitterø, Norway; Kola Peninsula, Russia.

How much is ambrinoite worth?+

Typical asking prices fall in the range of $50-300 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

Is ambrinoite safe to handle?+

This mineral is radioactive. Contains thorium, which is naturally radioactive. Store away from other radioactive-sensitive minerals and wash hands after handling to prevent ingestion of dust. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like ambrinoite?+

Ambrinoite is most often confused with Euxenite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with ambrinoite?+

Ambrinoite commonly co-occurs with Zircon, Monazite, Feldspar, Quartz. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does ambrinoite form in?+

Ambrinoite typically forms in granite pegmatites. Working float back to the host body is the standard way to chase a fresh occurrence.

What is ambrinoite used for?+

Ambrinoite is used in collector.

Find ambrinoite on the map

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