Magnetite

Hardness: 6-7 (Mohs scale), Color: Gray to black with yellowish-brown weathering, Luster: Submetallic, Crystal structure: Hexagonal prism, Cleavage: None (fractures conchoidally), Specific Gravity: 5.2-4.9

Magnetite commonly forms in igneous and metamorphic rocks. In igneous rocks, it crystallizes from molten magma. In metamorphic rocks, it forms under conditions of high temperature and pressure. It can also occur in sedimentary deposits due to weathering of iron-rich rocks. Geological age varies widely depending on the formation environment.

Predominantly used as an important iron ore for steel production. Also used as a heavy medium in coal washing, as a pigment, and in some specialized industrial applications due to its magnetic properties. Small, high-quality crystals are occasionally collected by mineral enthusiasts.

Magnetite is one of the most common iron ores and is famous for its natural magnetism. Lodestone, a naturally magnetized piece of magnetite, was used in early compasses. It can sometimes form perfectly octahedral crystals.

Key characteristics for field identification include its dark color (often black with a reddish-brown streak), high density, and strong magnetism (it will attract a magnet). It's commonly found in igneous intrusions, metamorphic terrains (like banded iron formations), and placer deposits. Collectors should look for well-formed crystals in pegmatites or skarns. It can be differentiated from hematite by its magnetic properties and black streak (hematite has a red or reddish-brown streak).