Rock Identifier
Probable magnetite-bearing rock (Magnetite (Fe₃O₄), possibly in a fine-grained host rock) — mineral
mineral

Probable magnetite-bearing rock

Magnetite (Fe₃O₄), possibly in a fine-grained host rock

AI-generated identification · may be incorrect

Small dark gray-to-black specimen with a metallic to submetallic luster and irregular fracture; magnetite has Mohs hardness 5.5–6.5, no cleavage, cubic crystal structure, and specific gravity about 5.2. The image is too low-resolution for confident identification or mineral testing.

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Physical properties

Small dark gray-to-black specimen with a metallic to submetallic luster and irregular fracture; magnetite has Mohs hardness 5.5–6.5, no cleavage, cubic crystal structure, and specific gravity about 5.2. The image is too low-resolution for confident identification or mineral testing.

Formation & geological history

Magnetite forms in igneous and metamorphic rocks, hydrothermal veins, and sedimentary iron deposits through oxidation–reduction processes. Its age depends on the host rock and may range from recent placer grains to Precambrian iron formations.

Uses & applications

Used as an iron ore, dense aggregate, pigment, and magnetic material; attractive crystals are collected but are generally not jewelry stones.

Geological facts

The strongest diagnostic property is magnetism: it should attract a strong magnet, often more strongly than hematite. A streak test on unglazed ceramic should produce a black streak.

Field identification & locations

Common in basalt, gabbro, metamorphic rocks, beach sands, and banded iron formations worldwide. Confirm with magnetism, black streak, and high density; the specimen could alternatively be another dark metallic mineral or slag.