Mottanaite-(Ce) is an extremely rare member of the hellandite group of silicates often found in miarolitic cavities within granitic pegmatites. It typically appears as brownish, prismatic crystals with a distinctive vitreous luster that can be confused with other rare-earth minerals like gadolinite.

Hardness

5.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineralrareHellandite Group family

Mottanaite-(Ce)

Hardness: 5.5
Luster: Vitreous
Streak: White
Transparency: Translucent

Is this mottanaite-(ce)?

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 mottanaite-(ce) with a known reference. Mottanaite-(Ce) sits at Mohs 5.5 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Mottanaite-(Ce) leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Mottanaite-(Ce) typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: brown, reddish-brown.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: prismatic crystals.

Often confused with

Mottanaite-(Ce) vs. its common look-alikes — and how to tell them apart in the field.

mineral

Gadolinite-(Y)

Mohs 6.5-7

How to tell apart: Gadolinite-(Y) is the harder of the two (Mohs 6.5-7 vs. 5.5).

Compare →

Often found alongside mottanaite-(ce)

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

All properties

Chemical formula: Ca₄Ce₂Zr(Be₂Si₄B₄O₂₂)O₂
Mohs hardness: 5.5
Density: 3.85 g/cm³
Colors: Brown Reddish-brown
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Prismatic Crystals
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Granite Pegmatites
Typical price: $50-300 per specimen

Where rockhounds find mottanaite-(ce)

Classic worldwide localities

Baveno, Italy
Mt. Malosa, Malawi

Field-hunting tip

Look in granite pegmatites country — that is the host setting where mottanaite-(ce) typically forms. If you start seeing fluorite, orthoclase, aegirine 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 mottanaite-(ce)?+

Mohs hardness is 5.5. It typically shows a vitreous luster. The streak is white. Common colors include brown, reddish-brown.

Where is mottanaite-(ce) found?+

Notable localities include Baveno, Italy; Mt. Malosa, Malawi.

How much is mottanaite-(ce) 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 mottanaite-(ce) safe to handle?+

This mineral is radioactive. Contains thorium as a common minor element; handle with care and wash hands after contact. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like mottanaite-(ce)?+

Mottanaite-(Ce) is most often confused with Gadolinite-(Y). A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with mottanaite-(ce)?+

Mottanaite-(Ce) commonly co-occurs with Fluorite, Orthoclase, Aegirine, Quartz. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does mottanaite-(ce) form in?+

Mottanaite-(Ce) typically forms in granite pegmatites. Working float back to the host body is the standard way to chase a fresh occurrence.

What is mottanaite-(ce) used for?+

Mottanaite-(Ce) is used in collector.

Find mottanaite-(ce) on the map

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