Althausite is a very rare magnesium phosphate mineral typically found in serpentinized ultramafic rocks. It often appears as small, colorless to white tabular crystals or massive aggregates and was first discovered in the Modum district of Norway.

Hardness

3.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrare

Althausite

Hardness: 3.5
Luster: Vitreous
Streak: White
Transparency: Transparent

Is this althausite?

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 althausite with a known reference. Althausite sits at Mohs 3.5 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Althausite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Althausite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: colorless, white, gray, pale yellow.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: tabular crystals, massive, granular.

Often confused with

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

mineral

Apatite

Mohs 5

How to tell apart: Apatite is the harder of the two (Mohs 5 vs. 3.5).

Often found alongside althausite

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

All properties

Chemical formula: Mg₄(PO₄)₂(OH,F)₂
Mohs hardness: 3.5
Density: 3.1 g/cm³
Colors: Colorless White Gray Pale Yellow
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Orthorhombic
Crystal habit: Tabular Crystals, Massive, Granular
Cleavage: Perfect On {001}
Rarity: Rare
Uses: Collector
Host rock: Serpentinite, Talc-carbonate Rocks
Typical price: $50-300 per specimen

Where rockhounds find althausite

Classic worldwide localities

Modum, Norway
Yukon Territory, Canada

Field-hunting tip

Look in serpentinite, talc-carbonate rocks country — that is the host setting where althausite typically forms. If you start seeing apatite, magnesite, holtedahlite 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 althausite?+

Mohs hardness is 3.5. It typically shows a vitreous luster. The streak is white. Common colors include colorless, white, gray, pale yellow.

Where is althausite found?+

Notable localities include Modum, Norway; Yukon Territory, Canada.

How much is althausite 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.

What rocks look like althausite?+

Althausite is most often confused with Apatite, Magnesite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with althausite?+

Althausite commonly co-occurs with Apatite, Magnesite, Holtedahlite, Szaibelyite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does althausite form in?+

Althausite typically forms in serpentinite, talc-carbonate rocks. Working float back to the host body is the standard way to chase a fresh occurrence.

What is althausite used for?+

Althausite is used in collector.

Find althausite on the map

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