Iowaite is a rare layered double hydroxide mineral typically found as green to blue-green platy aggregates in serpentinized rocks. It is highly unstable when exposed to air and can dehydrate or alter rapidly, making it a challenging but rewarding find for mineral collectors.

Hardness

1.5-2

Mohs

Luster

Pearly

Streak

White

Transparency

Translucent

mineralrareHydrotalcite Supergroup family

Iowaite

Hardness: 1.5-2
Luster: Pearly
Streak: White
Transparency: Translucent

Is this iowaite?

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 iowaite with a known reference. Iowaite sits at Mohs 1.5-2 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Iowaite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Iowaite typically shows a pearly luster.
4
Match the color range
Compare against the expected color range: green, blue-green.
5
Look at form & habit
Crystal system: trigonal. Typical habit: platy crystals, massive, or as vein fillings.

Often confused with

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

Often found alongside iowaite

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

All properties

Chemical formula: Mg₄Fe³⁺(OH)₈Cl·4H₂O
Mohs hardness: 1.5-2
Density: 2.1-2.2 g/cm³
Colors: Green Blue-green
Streak: White
Luster: Pearly
Transparency: Translucent
Crystal system: Trigonal
Crystal habit: Platy Crystals, Massive, Or as Vein Fillings
Cleavage: Perfect Basal
Rarity: Rare
Uses: Collector, Scientific Research
Host rock: Serpentinized Ultramafic Rocks
Typical price: $20-100 per specimen

Where rockhounds find iowaite

Classic worldwide localities

Iowa, USA
Tasmania, Australia
Quebec, Canada

Field-hunting tip

Look in serpentinized ultramafic rocks country — that is the host setting where iowaite typically forms. If you start seeing serpentine, magnetite, dolomite in float, you are in the right ground. Field specimens usually show a platy crystals, massive, or as vein fillings habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify iowaite?+

Mohs hardness is 1.5-2. It typically shows a pearly luster. The streak is white. Common colors include green, blue-green.

Where is iowaite found?+

Notable localities include Iowa, USA; Tasmania, Australia; Quebec, Canada.

How much is iowaite worth?+

Typical asking prices fall in the range of $20-100 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like iowaite?+

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

What minerals are found with iowaite?+

Iowaite commonly co-occurs with Serpentine, Magnetite, Dolomite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does iowaite form in?+

Iowaite typically forms in serpentinized ultramafic rocks. Working float back to the host body is the standard way to chase a fresh occurrence.

What is iowaite used for?+

Iowaite is used in collector, scientific research.

Find iowaite on the map

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