[13] Neodymium commonly exists in two allotropic forms, with a transformation from a double hexagonal to a body-centered cubic structure taking place at about 863 °C.

In the periodic table, it appears between the lanthanides praseodymium to its left and the radioactive element promethium to its right, and above the actinide uranium.

They are thus mostly restricted to the mostly ionic cyclopentadienides (isostructural with those of lanthanum) and the σ-bonded simple alkyls and aryls, some of which may be polymeric.

[28] In 1751, the Swedish mineralogist Axel Fredrik Cronstedt discovered a heavy mineral from the mine at Bastnäs, later named cerite.

Thirty years later, fifteen-year-old Wilhelm Hisinger, a member of the family owning the mine, sent a sample to Carl Scheele, who did not find any new elements within.

In 1803, after Hisinger had become an ironmaster, he returned to the mineral with Jöns Jacob Berzelius and isolated a new oxide, which they named ceria after the dwarf planet Ceres, which had been discovered two years earlier.

[32][33][34] He partially decomposed a sample of cerium nitrate by roasting it in air and then treating the resulting oxide with dilute nitric acid.

The name neodymium is derived from the Greek words neos (νέος), new, and didymos (διδύμος), twin.

Starting in the 1950s, high purity (>99%) neodymium was primarily obtained through an ion exchange process from monazite, a mineral rich in rare-earth elements.

[41] The main mining areas are in China, United States, Brazil, India, Sri Lanka, and Australia.

As a result, it tends to occur along with them in phosphate, silicate and carbonate minerals, such as monazite (MIIIPO4) and bastnäsite (MIIICO3F), where M refers to all the rare-earth metals except scandium and the radioactive promethium (mostly Ce, La, and Y, with somewhat less Pr and Nd).

The ore, after being crushed and ground, is first treated with hot concentrated sulfuric acid, which liberates carbon dioxide, hydrogen fluoride, and silicon tetrafluoride.

The product is then dried and leached with water, leaving the early lanthanide ions, including lanthanum, in solution.

[43][44] Neodymium is classified as a lithophile under the Goldschmidt classification, meaning that it is generally found combined with oxygen.

Historically, the Chinese government imposed strategic material controls on the element, causing large fluctuations in prices.

[45] The uncertainty of pricing and availability have caused companies (particularly Japanese ones) to create permanent magnets and associated electric motors with fewer rare-earth metals; however, so far they have been unable to eliminate the need for neodymium.

[46][47] According to the US Geological Survey, Greenland holds the largest reserves of undeveloped rare-earth deposits, particularly neodymium.

[48] Neodymium is typically 10–18% of the rare-earth content of commercial deposits of the light rare-earth-element minerals bastnäsite and monazite.

Outstanding examples of this include monazite crystals from the tin deposits in Llallagua, Bolivia; ancylite from Mont Saint-Hilaire, Quebec, Canada; or lanthanite from Lower Saucon Township, Pennsylvania.

The absorption bands of neodymium interact with the visible emission spectrum of mercury vapor, with the unfiltered shortwave UV light causing neodymium-containing minerals to reflect a distinctive green color.

This can be observed with monazite-containing sands or bastnäsite-containing ore.[49] The demand for mineral resources, such as rare-earth elements (including neodymium) and other critical materials, has been rapidly increasing owing to the growing human population and industrial development.

Recently, the requirement for a low-carbon society has led to a significant demand for energy-saving technologies such as batteries, high-efficiency motors, renewable energy sources, and fuel cells.

Toward achieving the objectives of the Paris Agreement, the demand for NdFeB magnets is expected to increase significantly in the future.

A neodymium magnet of a few tens of grams can lift a thousand times its own weight, and can snap together with enough force to break bones.

[55] For example, drive electric motors of each Toyota Prius require one kilogram (2.2 pounds) of neodymium per vehicle.

Neodymium may be used to color glass in shades ranging from pure violet through wine-red and warm gray.

[56] The first commercial use of purified neodymium was in glass coloration, starting with experiments by Leo Moser in November 1927.

The similar absorption of the yellow mercury emission line at 578 nm is the principal cause of the blue color observed for neodymium glass under traditional white-fluorescent lighting.

The success of the Nd3+ ion lies in the structure of its energy levels and in the spectroscopic properties suitable for the generation of laser radiation.

This has led to an estimated 1,700 emergency room visits[86] and necessitated the recall of the Buckyballs line of toys, which were construction sets of small neodymium magnets.