Magnetite Identification Guide
A field guide to identifying Magnetite, iron oxide, by its strong magnetism, black streak, metallic luster, and octahedra.
Read the full Magnetite encyclopedia entry →
What Magnetite Looks Like
Magnetite is iron oxide (Fe3O4), one of the most easily identified minerals because of its strong magnetism. It is a dense, black, metallic mineral and a major iron ore. Naturally magnetized pieces are called lodestone.
- Color: iron-black
- Luster: metallic to submetallic
- Transparency: opaque
- Habit: octahedral crystals (eight-sided), also massive, granular, and as black sand grains
Step-by-Step Field ID Checklist
- Bring a magnet close — magnetite is strongly attracted; this alone nearly confirms it.
- Check the color and luster — iron-black with a metallic shine.
- Streak it on unglazed porcelain — a black streak (distinguishing it from hematite's red-brown streak).
- Look for octahedral crystal form if crystals are present.
- Heft it — magnetite is dense and feels heavy (SG ~5.2).
Key Diagnostic Tests
- Magnetism: strongly magnetic — the single most diagnostic property.
- Mohs hardness: 5.5-6.5.
- Streak: black.
- Cleavage: none; fracture is conchoidal to uneven; octahedral parting may occur.
- Specific gravity: ~5.1-5.2, distinctly heavy.
Common Look-Alikes and How to Tell Them Apart
- Hematite: can be steely-black, but hematite gives a red-brown streak and is only weakly (or not) magnetic; magnetite gives a black streak and is strongly magnetic.
- Chromite: brownish-black with a brown streak and only weakly magnetic; magnetite is more strongly magnetic with black streak.
- Ilmenite: black, weakly magnetic, brown-black streak; magnetism and streak separate it.
- Franklinite: similar look but weakly magnetic; usually found with zinc minerals at Franklin, NJ.
Where It Is Typically Found
Magnetite is widespread — in igneous and metamorphic rocks, banded iron formations, and as heavy black sand in stream and beach placers. Major deposits occur in Sweden (Kiruna), Russia, the USA, and many other regions.
Frequently asked questions
How can you tell if a rock is magnetite?
Magnetite is iron-black, metallic, dense (SG ~5.2), gives a black streak, and is strongly attracted to a magnet. The strong magnetism plus black streak make identification straightforward.
Magnetite vs hematite - what's the difference?
Both are iron oxides and can look black, but magnetite is strongly magnetic with a black streak, while hematite is weakly or non-magnetic and gives a red-brown streak. The streak test is decisive.
Is magnetite the same as lodestone?
Lodestone is a naturally permanently magnetized variety of magnetite that acts like a magnet and attracts iron filings. All lodestone is magnetite, but only some magnetite is magnetized as lodestone.
What does magnetite look like?
It is an opaque, iron-black mineral with a metallic luster, often forming eight-sided octahedral crystals or occurring as heavy black sand grains.
Magnetite identified by the community
Recent Magnetite specimens identified with Rock Identifier.
