Monazite-(Sm) is a very rare rare-earth phosphate mineral belonging to the monazite group. It typically occurs as small crystals in complex pegmatites and is highly prized by collectors for its chemical specificity, despite being mildly radioactive due to thorium impurities.

Hardness

5-5.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineralrareMonazite Group family

Monazite-(Sm)

Hardness: 5-5.5
Luster: Vitreous
Streak: White
Transparency: Translucent

No image

Is this monazite-(sm)?

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

Often confused with

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

mineral

Monazite-(Ce)

Mohs 5-5.5

How to tell apart: Luster reads vitreous on Monazite-(Sm) and resinous on Monazite-(Ce).

How to tell apart: Zircon is the harder of the two (Mohs 7.5 vs. 5-5.5); luster reads vitreous on Monazite-(Sm) and adamantine on Zircon.

Often found alongside monazite-(sm)

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

All properties

Chemical formula: (Sm,Ce,Gd)PO₄
Mohs hardness: 5-5.5
Density: 5.1-5.3 g/cm³
Colors: Yellow Brown Reddish-brown
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Prismatic Crystals, Granular, Massive
Cleavage: Distinct On {100}
Rarity: Rare
Uses: Collector
Host rock: Granite Pegmatites, Rare-earth Element Enriched Alkaline Rocks
Typical price: $50-300 per specimen

Where rockhounds find monazite-(sm)

Classic worldwide localities

Norway
Russia
China
Canada

Field-hunting tip

Look in granite pegmatites, rare-earth element enriched alkaline rocks country — that is the host setting where monazite-(sm) typically forms. If you start seeing quartz, feldspar, biotite in float, you are in the right ground. Field specimens usually show a prismatic crystals, granular, massive habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify monazite-(sm)?+

Mohs hardness is 5-5.5. It typically shows a vitreous luster. The streak is white. Common colors include yellow, brown, reddish-brown.

Where is monazite-(sm) found?+

Notable localities include Norway; Russia; China; Canada.

How much is monazite-(sm) 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 monazite-(sm) safe to handle?+

This mineral is radioactive. Contains thorium and uranium trace elements; store in a shielded container or away from living areas and handle with care, avoiding inhalation of dust. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like monazite-(sm)?+

Monazite-(Sm) is most often confused with Monazite-(Ce), Zircon, Xenotime. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with monazite-(sm)?+

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

What kind of rock does monazite-(sm) form in?+

Monazite-(Sm) typically forms in granite pegmatites, rare-earth element enriched alkaline rocks. Working float back to the host body is the standard way to chase a fresh occurrence.

What is monazite-(sm) used for?+

Monazite-(Sm) is used in collector.

Find monazite-(sm) on the map

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