Horomanite is an extremely rare potassium-nickel silicate mineral discovered within the Horoman peridotite complex in Japan. It typically occurs as small, anhedral grains intergrown within mantle-derived ultramafic rocks and is of significant interest to mineralogical researchers due to its unique chemical composition.
Is this horomanite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch horomanite with a known reference. Horomanite sits at Mohs 5-6 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Horomanite leaves a yellowish-white streak.
- 3Read the lusterHold the specimen under a strong light. Horomanite typically shows a submetallic luster.
- 4Match the color rangeCompare against the expected color range: brown, yellowish-brown.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: anhedral grains.
Often confused with
Horomanite vs. its common look-alikes — and how to tell them apart in the field.
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
- KNi₄Si₂O₇
- Mohs hardness
- 5-6
- Density
- 4.15 g/cm³
- Colors
- Streak
- Yellowish-white
- Luster
- Submetallic
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Anhedral Grains
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Peridotite
- Typical price
- n/a
Where rockhounds find horomanite
Classic worldwide localities
- Horoman River, Hokkaido, Japan
Field-hunting tip
Look in peridotite country — that is 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 anhedral grains habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find horomanite on the map
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