Horomanite is a rare iron nickel sulfide that forms grains. It is a filling space between silicate minerals in lherzolites of a peridotite massif. It was first described from Horoman peridotite massif, Samani-cho, Samani-gun, Hokkaido, Japan.

Hardness

Mohs

Luster

Metallic

Streak

Yellowish-white

Transparency

Opaque

mineralrare

Horomanite

Hardness: 3
Luster: Metallic
Streak: Yellowish-white
Transparency: Opaque

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Is this horomanite?

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 horomanite with a known reference. Horomanite sits at Mohs 3, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Horomanite leaves a yellowish-white streak.
3
Read the luster
Hold the specimen under a strong light. Horomanite typically shows a metallic luster.
4
Match the color range
Compare against the expected color range: brown, yellowish-brown.
5
Look at form & habit
Crystal system: tetragonal. Typical habit: grains.

Often confused with

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

mineral

Kalsilite

Mohs 6

How to tell apart: Kalsilite is the harder of the two (Mohs 6 vs. 3); streak differs, so Horomanite leaves yellowish-white, Kalsilite leaves white; luster reads metallic on Horomanite and vitreous on Kalsilite.

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Often found alongside horomanite

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

All properties

Chemical formula: Fe₆Ni₃S₈
Mohs hardness: 3
Density: 6.44 g/cm³
Colors: Brown Yellowish-brown
Streak: Yellowish-white
Luster: Metallic
Transparency: Opaque
Crystal system: Tetragonal
Crystal habit: Grains
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Peridotite

Where rockhounds find horomanite

Classic worldwide localities

Horoman River, Hokkaido, Japan

Field-hunting tip

Look in peridotite country, the host setting where horomanite typically forms. If you start seeing olivine, orthopyroxene, clinopyroxene in float, you are in the right ground. Field specimens usually show a grains habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify horomanite?+

Mohs hardness is 3. It typically shows a metallic luster. The streak is yellowish-white. Common colors include brown, yellowish-brown.

Where is horomanite found?+

Notable localities include Horoman River, Hokkaido, Japan.

What rocks look like horomanite?+

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

What minerals are found with horomanite?+

Horomanite commonly co-occurs with Olivine, Orthopyroxene, Clinopyroxene, Chromite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does horomanite form in?+

Horomanite typically forms in peridotite. Working float back to the host body is the standard way to chase a fresh occurrence.

What is horomanite used for?+

Horomanite is used in collector.

Find horomanite on the map

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