Magnesioferrite is a member of the spinel group that appears as black, metallic, octahedral crystals. It is typically found in high-temperature volcanic environments like fumaroles or within metamorphosed limestones. It is strongly magnetic, though often less so than magnetite, and lacks any discernible cleavage.
Is this magnesioferrite?
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 magnesioferrite with a known reference. Magnesioferrite sits at Mohs 6-6.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Magnesioferrite leaves a black streak.
- 3Read the lusterHold the specimen under a strong light. Magnesioferrite typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: black.
- 5Look at form & habitCrystal system: cubic. Typical habit: octahedral crystals, massive.
Often confused with
Magnesioferrite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Magnesioferrite leaves black, Chromite leaves dark brown; luster reads metallic on Magnesioferrite and submetallic on Chromite.
How to tell apart: Streak differs — Magnesioferrite leaves black, Franklinite leaves reddish-brown.
Often found alongside magnesioferrite
Minerals reported to co-occur with magnesioferrite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- MgFe³⁺₂O₄
- Mohs hardness
- 6-6.5
- Density
- 4.5-4.6 g/cm³
- Colors
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Cubic
- Crystal habit
- Octahedral Crystals, Massive
- Cleavage
- None
- Rarity
- Uncommon
- Uses
- Collector, Scientific Research
- Host rock
- Fumaroles, Contact Metamorphic Limestones, Kimberlites
- Typical price
- $15-100 per specimen
Where rockhounds find magnesioferrite
Classic worldwide localities
- Mount Vesuvius, Italy
- Kola Peninsula, Russia
- Iron Mountains, California, USA
- Jacupiranga, Brazil
Field-hunting tip
Look in fumaroles, contact metamorphic limestones, kimberlites country — that is the host setting where magnesioferrite typically forms. If you start seeing magnetite, hematite, forsterite in float, you are in the right ground. Field specimens usually show a octahedral crystals, massive habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find magnesioferrite on the map
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