Carbonyl iron, Dnipropetrovsk region.

"
Carbonyl iron is a high-purity (97.5% for S grade, 99.5+% for R grade) iron obtained by chemical decomposition of purified iron pentacarbonyl. Usually it has the form of a gray powder consisting of spherical microparticles. Most impurities are carbon, oxygen and nitrogen. In electronics, carbonyl iron is used for the production of magnetic cores and for the production of some ferrites. Spherical particles made of carbonyl iron are used as a component of radio-absorbing materials used in the armed forces, for example, in stealth vehicles. Other applications - in powder metallurgy, metal casting under pressure and in various specialized products.

Powder cores made of carbonyl iron have high stability of parameters in a wide range of temperatures and levels of magnetic flux, with excellent Q-factor in the range from 50 kHz to 200 MHz. . A popular application is broadband inductors, especially in high-power applications.
(//tractor-service.com)
In pharmaceuticals, carbonyl iron powder is used to treat iron deficiency and as adietary supplement with iron. In 2017, carbonyl iron powder was registered as an effective reducer of aromatic nitro groups in water, an important reaction used in the synthesis of pharmaceutical drugs.

Particles of carbonyl iron (20-40%), suspended in a carrier liquid (60-80%) are used as a magnetorheological fluid.

"