Nickel-iron is a nickel-iron alloy with a nickel content of 19%-59%. The melting point of nickel-iron is 1430-1480 degrees, and its density is 8.15-8.43. The main components of nickel-iron are nickel and iron, and it also contains a small amount of cobalt. The mineral's fracture is jagged, it is uncommon, occurring in massive, granular aggregates, appearing iron-grey, dark grey, or black, with a streak of iron grey, opaque, and a fresh surface showing metallic luster. Nickel-iron also contains impurities such as carbon, silicon, sulfur, phosphorus, chromium, and copper. It is mainly used as a nickel additive for steel and cast iron production. According to the international standard (ISO), nickel-iron is classified by nickel content into FeNi20 (15%–25% Ni), FeNi30 (25%–35% Ni), FeNi40 (35%–45% Ni), and FeNi50 (45%–60% Ni). It is further divided into high carbon (1.0%–2.5% C), medium carbon (0.030%–1.0% C), and low carbon (<0.03%C); low-phosphorus (<0.02%P) and high-phosphorus (<0.030%P) ferronickel. In both liquid and solid states, nickel and iron dissolve in each other in any proportion.

Serrated fractures, uncommon in this mineral, produced in lump or granular aggregates. Iron gray, dark gray or black, streaked iron gray. Opaque, fresh surface shows metallic luster.