mineral
Magnetite-rich iron ore
Magnetite (Fe₃O₄), possibly massive magnetite/ironstone
AI-generated identification · may be incorrectBlack to dark gray, submetallic to metallic luster, uneven fracture, opaque, and typically Mohs hardness 5.5–6.5; specific gravity about 5.2. It is commonly strongly magnetic, though the image alone cannot confirm magnetism.
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Physical properties
Black to dark gray, submetallic to metallic luster, uneven fracture, opaque, and typically Mohs hardness 5.5–6.5; specific gravity about 5.2. It is commonly strongly magnetic, though the image alone cannot confirm magnetism.
Formation & geological history
Forms in igneous and metamorphic environments, including mafic intrusions, contact-metamorphic skarns, and banded iron formations; deposits range from Archean to recent geological ages. The specimen appears natural and unpolished, with a rough massive texture.
Uses & applications
Major industrial iron ore and a source of iron-based pigments; attractive crystalline specimens are collected, but it is rarely used as a gemstone.
Geological facts
Magnetite is the naturally magnetic iron oxide responsible for lodestone. Its black streak and attraction to a magnet distinguish it from many visually similar dark rocks.
Field identification & locations
Test with a strong magnet, streak it on unglazed porcelain for a black streak, and compare its unusually high density; common sources include Sweden, the United States, Canada, Brazil, and Australia.
