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. Streak: black.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic to semimetallic, may be dull.
- 4Match the color rangeCompare against the expected color range: black, brownish black.
- 5Look at form & habitCrystal system: cubic. Typical habit: crystalline, 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 brown.
How to tell apart: Streak differs, so Magnesioferrite leaves black, Franklinite leaves reddish brown to black.
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
- 4.55-4.65 g/cm³
- Colors
- Streak
- Black
- Luster
- Metallic to semimetallic, may be dull
- Transparency
- Opaque, transparent in thin fragments
- Crystal system
- Cubic
- Crystal habit
- Crystalline, massive
- Cleavage
- {111} parting likely
- Rarity
- Uncommon
- Uses
- Collector, Scientific research
- Host rock
- Most commonly of fumarolic origin; also in high-grade (sanidinite facies) combustion-metamorphosed marls and burning coal heaps; in metamorphosed dolostones
Where rockhounds find magnesioferrite
Classic worldwide localities
- Crestmore quarry, Riverside Co., California and at Magnet Cove, Hot Spring Co., Arkansas, USA
- Vesuvius and Monte Somma, Campania, Italy
- Etna, Sicily, Italy
- Stromboli and Vulcano, Lipari Islands, Italy
- Puy de la Tache, Mont Dore, Puy-de-Dôme, France
- Hatrurim Formation, Israel
Field-hunting tip
Where it forms: Most commonly of fumarolic origin; also in high-grade (sanidinite facies) combustion-metamorphosed marls and burning coal heaps; in metamorphosed dolostones. If you start seeing hematite, titanian magnetite, ferrian diopside in float, you are in the right ground. Typical habit: crystalline, massive. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify magnesioferrite?+
Where is magnesioferrite found?+
What rocks look like magnesioferrite?+
What minerals are found with magnesioferrite?+
What kind of rock does magnesioferrite form in?+
What is magnesioferrite used for?+
Find magnesioferrite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
