Angastonite is a very rare hydrated calcium magnesium aluminum phosphate mineral. It typically occurs as small, delicate platy crystal aggregates within phosphate-rich zones in marble deposits.

Hardness

Mohs

Luster

Pearly

Streak

White

Transparency

Translucent

mineralrare

Angastonite

Angastonite is a very rare hydrated calcium magnesium aluminum phosphate mineral. It typically occurs as small, delicate platy crystal aggregates within phosphate-rich zones in marble deposits.

Hardness: 2
Luster: Pearly
Streak: White
Transparency: Translucent

Is this angastonite?

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

Often confused with

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

mineral

Wavellite

Mohs 3.5-4

How to tell apart: Wavellite is the harder of the two (Mohs 3.5-4 vs. 2); luster reads pearly on Angastonite and vitreous on Wavellite.

How to tell apart: Variscite is the harder of the two (Mohs 3.5-4.5 vs. 2); luster reads pearly on Angastonite and waxy on Variscite.

Compare →

Often found alongside angastonite

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

All properties

Chemical formula: CaMgAl₂(PO₄)₂(OH)₄·7H₂O
Mohs hardness: 2
Density: 2.16 g/cm³
Colors: White Colorless
Streak: White
Luster: Pearly
Transparency: Translucent
Crystal system: Triclinic
Crystal habit: Platy Crystals
Cleavage: Perfect
Rarity: Rare
Uses: Collector
Host rock: Phosphate-rich Deposits in Marble
Typical price: $50-300 per specimen

Where rockhounds find angastonite

Classic worldwide localities

Angaston, South Australia, Australia

Field-hunting tip

Look in phosphate-rich deposits in marble country, the host setting where angastonite typically forms. If you start seeing apatite, dolomite, quartz in float, you are in the right ground. Field specimens usually show a platy crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify angastonite?+

Mohs hardness is 2. It typically shows a pearly luster. The streak is white. Common colors include white, colorless.

Where is angastonite found?+

Notable localities include Angaston, South Australia, Australia.

How much is angastonite 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 angastonite?+

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

What minerals are found with angastonite?+

Angastonite commonly co-occurs with Apatite, Dolomite, Quartz. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does angastonite form in?+

Angastonite typically forms in phosphate-rich deposits in marble. Working float back to the host body is the standard way to chase a fresh occurrence.

What is angastonite used for?+

Angastonite is used in collector.

Find angastonite on the map

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