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, so Magnesioferrite leaves black, Chromite leaves dark brown; luster reads metallic on Magnesioferrite and submetallic on Chromite.
How to tell apart: Streak differs, so 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, 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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What rocks look like magnesioferrite?+
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Find magnesioferrite on the map
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