Thorasphite is a rare thorium silicate mineral that occurs as distinct, transparent tetragonal prisms. It is primarily found in specialized alkaline pegmatite environments and is highly sought after by radioactive mineral collectors due to its scarcity and chemical composition.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Thorasphite

Hardness: 4
Luster: Vitreous
Streak: White
Transparency: Transparent

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Is this thorasphite?

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 thorasphite with a known reference. Thorasphite sits at Mohs 4 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Thorasphite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Thorasphite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: white, colorless.
5
Look at form & habit
Crystal system: tetragonal. Typical habit: prismatic crystals.

Often confused with

Thorasphite 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 — Thorasphite leaves white, Thorite leaves dark brown; luster reads vitreous on Thorasphite and resinous on Thorite.

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Often found alongside thorasphite

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

All properties

Chemical formula: ThSiO₄
Mohs hardness: 4
Density: 5.45 g/cm³
Colors: White Colorless
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Tetragonal
Crystal habit: Prismatic Crystals
Cleavage: Distinct
Rarity: Rare
Uses: Collector
Host rock: Alkaline Pegmatites
Typical price: $100-500 thumbnail

Where rockhounds find thorasphite

Classic worldwide localities

Norway

Field-hunting tip

Look in alkaline pegmatites country — that is the host setting where thorasphite typically forms. If you start seeing zircon, fluorite, quartz 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 thorasphite?+

Mohs hardness is 4. It typically shows a vitreous luster. The streak is white. Common colors include white, colorless.

Where is thorasphite found?+

Notable localities include Norway.

How much is thorasphite worth?+

Typical asking prices fall in the range of $100-500 thumbnail. Quality, size, and provenance can move individual specimens well outside that range.

Is thorasphite safe to handle?+

This mineral is radioactive. It contains toxic constituents. Thorasphite contains thorium, a radioactive element, and should be handled with caution. Keep in a sealed lead-lined container and avoid inhalation or ingestion of dust particles. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like thorasphite?+

Thorasphite 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 thorasphite?+

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

What kind of rock does thorasphite form in?+

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

What is thorasphite used for?+

Thorasphite is used in collector.

Find thorasphite on the map

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