Magnetite in the context of "Burgas Bay"

A magnet is a material or object that produces a magnetic field. This magnetic field is invisible but is responsible for the most notable property of a magnet: a force that pulls on other ferromagnetic materials, such as iron, steel, nickel, cobalt, etc. and attracts or repels other magnets.

A permanent magnet is an object made from a material that is magnetized and creates its own persistent magnetic field. An everyday example is a refrigerator magnet used to hold notes on a refrigerator door. Materials that can be magnetized, which are also the ones that are strongly attracted to a magnet, are called ferromagnetic (or ferrimagnetic). These include the elements iron, nickel and cobalt and their alloys, some alloys of rare-earth metals, and some naturally occurring minerals such as lodestone. Although ferromagnetic (and ferrimagnetic) materials are the only ones attracted to a magnet strongly enough to be commonly considered magnetic, all other substances respond weakly to a magnetic field, by one of several other types of magnetism.

Iron ores are rocks and minerals from which metallic iron can be economically extracted. The ores are usually rich in iron oxides and vary in color from dark grey, bright yellow, or deep purple to rusty red. The iron is usually found in the form of magnetite (Fe
₃O
₄, 72.4% Fe), hematite (Fe
₂O
₃, 69.9% Fe), goethite (FeO(OH), 62.9% Fe), limonite (FeO(OH)·n(H₂O), 55% Fe), or siderite (FeCO₃, 48.2% Fe).

Ores containing very high quantities of hematite or magnetite (typically greater than about 60% iron) are known as natural ore or [direct shipping ore], and can be fed directly into iron-making blast furnaces. Iron ore is the raw material used to make pig iron, which is one of the primary raw materials to make steel — 98% of the mined iron ore is used to make steel. In 2011 the Financial Times quoted Christopher LaFemina, mining analyst at Barclays Capital, saying that iron ore is "more integral to the global economy than any other commodity, except perhaps oil".

Peperino is an Italian word describing a brown or grey volcanic tuff, containing fragments of basalt and limestone, with disseminated crystals of augite, mica, magnetite, leucite, and other similar minerals. The name originally referred to the dark-colored inclusions, suggestive of peppercorns.

The typical peperino occurs in the Alban Hills and in Soriano nel Cimino, near Rome, and was used by the ancient Romans under the name of lapis albanus as a building stone and for the basins of fountains.

Ironstone is a sedimentary rock, either deposited directly as a ferruginous sediment or created by chemical replacement, that contains a substantial proportion of an iron ore compound from which iron (Fe) can be smelted commercially.

Not to be confused with native or telluric iron, which is very rare and found in metallic form, the term ironstone is customarily restricted to hard, coarsely banded, non-banded, and non-cherty sedimentary rocks of post-Precambrian age. The Precambrian deposits, which have a different origin, are generally known as banded iron formations. The iron minerals comprising ironstones can consist either of oxides, i.e. limonite, hematite, and magnetite; carbonates, i.e. siderite; silicates, i.e. chamosite; or some combination of these minerals.

Anorthosite (/əˈnɔːrθəsaɪt/) is a phaneritic, intrusive igneous rock characterized by its composition: mostly plagioclase feldspar (90–100%), with a minimal mafic component (0–10%). Pyroxene, ilmenite, magnetite, and olivine are the mafic minerals most commonly present.

Anorthosites are of enormous geologic interest, because it is still not fully understood how they form. Most models involve separating plagioclase crystals based on their density. Plagioclase crystals are usually less dense than magma; so, as plagioclase crystallizes in a magma chamber, the plagioclase crystals float to the top, concentrating there.

Rock magnetism is the study of the magnetic properties of rocks, sediments and soils. The field arose out of the need in paleomagnetism to understand how rocks record the Earth's magnetic field. This remanence is carried by minerals, particularly certain strongly magnetic minerals like magnetite (the main source of magnetism in lodestone). An understanding of remanence helps paleomagnetists to develop methods for measuring the ancient magnetic field and correct for effects like sediment compaction and metamorphism. Rock magnetic methods are used to get a more detailed picture of the source of the distinctive striped pattern in marine magnetic anomalies that provides important information on plate tectonics. They are also used to interpret terrestrial magnetic anomalies in magnetic surveys as well as the strong crustal magnetism on Mars.

Strongly magnetic minerals have properties that depend on the size, shape, defect structure and concentration of the minerals in a rock. Rock magnetism provides non-destructive methods for analyzing these minerals such as magnetic hysteresis measurements, temperature-dependent remanence measurements, Mössbauer spectroscopy, ferromagnetic resonance and so on. With such methods, rock magnetists can measure the effects of past climate change and human impacts on the mineralogy (see environmental magnetism). In sediments, a lot of the magnetic remanence is carried by minerals that were created by magnetotactic bacteria, so rock magnetists have made significant contributions to biomagnetism.

Ore grade is a measure describing the concentration of a commodity (e.g. metal or minerals) in ore. For metals sold in oxide form (such as tungsten and uranium), the grade may describe the percentage of oxide content (WO
₃ and U
₂O
₈ respectively).

Ore grade is used to assess the economic feasibility of a mining operation; the concentration of the commodity must be high enough so that it outweighs the cost of extracting it. The ore grade required for economic feasibility varies widely based on the value of the material being mined. The lowest grade that is feasible to mine is called a cut-off grade and is determined using various economic and political considerations.