Otwayite is a rare nickel carbonate mineral that typically appears as bright green, fibrous crusts or micro-crystalline aggregates. It is most commonly found in the oxidized zones of nickel sulfide deposits in Western Australia, often associated with other rare nickel minerals like gaspeite. Due to its scarcity and distinct coloration, it is highly sought after by systematic mineral collectors.

Hardness

Mohs

Luster

Silky to waxy

Streak

Light green

Transparency

Opaque to translucent

mineralrare

Otwayite

Hardness: 4
Luster: Silky to waxy
Streak: Light green
Transparency: Opaque to translucent

Is this otwayite?

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 otwayite with a known reference. Otwayite 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. Streak: light green.
3
Read the luster
Hold the specimen under a strong light. Luster: silky to waxy.
4
Match the color range
Compare against the expected color range: bright green, green.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: aggregates, fibrous.

Often confused with

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

mineral

Zaratite

Mohs 3.5

How to tell apart: Luster reads silky to waxy on Otwayite and vitreous to greasy on Zaratite.

Compare →

Often found alongside otwayite

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

All properties

Chemical formula: Ni₂CO₃(OH)₂·H₂O
Mohs hardness: 4
Density: 3.41 g/cm³
Colors: Bright green Green
Streak: Light green
Luster: Silky to waxy
Transparency: Opaque to translucent
Crystal system: Orthorhombic
Crystal habit: Aggregates, fibrous
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: In veinlets in serpentinite (Otway prospect, Western Australia; Lord Brassey mine, Tasmania, Australia)

Where rockhounds find otwayite

Classic worldwide localities

Otway Ni prospect, 23 km north of the town of Nullagine, Pilbara region, Western Australia (type locality)

Field-hunting tip

Where it forms: In veinlets in serpentinite (Otway prospect, Western Australia; Lord Brassey mine, Tasmania, Australia). If you start seeing magnesite, pecoraite, gaspéite in float, you are in the right ground. Typical habit: aggregates, fibrous. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify otwayite?+

Mohs hardness is 4. Luster: silky to waxy. The streak is light green. Common colors include bright green, green.

Where is otwayite found?+

Notable localities include Otway Ni prospect, 23 km north of the town of Nullagine, Pilbara region, Western Australia (type locality).

Is otwayite safe to handle?+

Otwayite contains nickel. Contains nickel, which is a toxic heavy metal; wash hands thoroughly after handling specimens and avoid inhaling dust.

What rocks look like otwayite?+

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

What minerals are found with otwayite?+

Otwayite commonly co-occurs with Magnesite, Pecoraite, Gaspéite, Paraotwayite, Millerite, Polydymite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does otwayite form in?+

Where it forms: In veinlets in serpentinite (Otway prospect, Western Australia; Lord Brassey mine, Tasmania, Australia). Working float back to the host body is the standard way to chase a fresh occurrence.

What is otwayite used for?+

Otwayite is used in collector.

Find otwayite on the map

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