Thorosteenstrupine is a rare thorium-rich silicate mineral typically found in highly alkaline igneous complexes. It is closely related to the steenstrupine group and is valued primarily by advanced mineral collectors due to its distinct radioactivity and locality-specific occurrence.

Hardness

4.5-5

Mohs

Luster

Vitreous

Streak

Yellowish-white

Transparency

Translucent

mineralrareSteenstrupine Group family

Thorosteenstrupine

Hardness: 4.5-5
Luster: Vitreous
Streak: Yellowish-white
Transparency: Translucent

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Is this thorosteenstrupine?

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 thorosteenstrupine with a known reference. Thorosteenstrupine sits at Mohs 4.5-5 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Thorosteenstrupine leaves a yellowish-white streak.
3
Read the luster
Hold the specimen under a strong light. Thorosteenstrupine typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: brown, yellow, reddish-brown.
5
Look at form & habit
Crystal system: trigonal. Typical habit: tabular crystals, massive, granular.

Often confused with

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

mineral

Thorite

Mohs 4.5-5

How to tell apart: Streak differs — Thorosteenstrupine leaves yellowish-white, Thorite leaves dark brown; luster reads vitreous on Thorosteenstrupine and resinous on Thorite.

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Often found alongside thorosteenstrupine

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

All properties

Chemical formula: (Ca,Th,Mn)₂(Si,P,Al)₄O₁₁(OH,F)₂·nH₂O
Mohs hardness: 4.5-5
Density: 3.3-3.6 g/cm³
Colors: Brown Yellow Reddish-brown
Streak: Yellowish-white
Luster: Vitreous
Transparency: Translucent
Crystal system: Trigonal
Crystal habit: Tabular Crystals, Massive, Granular
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Alkaline Pegmatites
Typical price: $50-300 per specimen depending on size and quality

Where rockhounds find thorosteenstrupine

Classic worldwide localities

Ilimaussaq Complex, Greenland
Kola Peninsula, Russia

Field-hunting tip

Look in alkaline pegmatites country — that is the host setting where thorosteenstrupine typically forms. If you start seeing eudialyte, microcline, aegirine in float, you are in the right ground. Field specimens usually show a tabular crystals, massive, granular habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify thorosteenstrupine?+

Mohs hardness is 4.5-5. It typically shows a vitreous luster. The streak is yellowish-white. Common colors include brown, yellow, reddish-brown.

Where is thorosteenstrupine found?+

Notable localities include Ilimaussaq Complex, Greenland; Kola Peninsula, Russia.

How much is thorosteenstrupine worth?+

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

Is thorosteenstrupine safe to handle?+

This mineral is radioactive. This mineral contains thorium and is radioactive; handle with care, use gloves, and store in a lead-lined or secure container away from living spaces. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like thorosteenstrupine?+

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

What minerals are found with thorosteenstrupine?+

Thorosteenstrupine commonly co-occurs with Eudialyte, Microcline, Aegirine, Sodalite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does thorosteenstrupine form in?+

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

What is thorosteenstrupine used for?+

Thorosteenstrupine is used in collector.

Find thorosteenstrupine on the map

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