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
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 anhedral grains habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify horomanite?+
Where is horomanite found?+
What rocks look like horomanite?+
What minerals are found with horomanite?+
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Find horomanite on the map
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