cobalt

American  

[koh-bawlt] / ˈkoʊ bɔlt /

noun

1. a silver-white metallic element with a faint pinkish tinge, occurring in compounds whose silicates afford important blue coloring substances for ceramics. Co; 58.933; 27; 8.9 at 20°C.

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cobalt British  

/ ˈkəʊbɔːlt /

noun

1. a brittle hard silvery-white element that is a ferromagnetic metal: occurs principally in cobaltite and smaltite and is widely used in alloys. The radioisotope cobalt-60 , with a half-life of 5.3 years, is used in radiotherapy and as a tracer. Symbol: Co; atomic no: 27; atomic wt: 58.93320; valency: 2 or 3; relative density: 8.9; melting pt: 1495°C; boiling pt: 2928°C

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cobalt Scientific  

/ kō′bôlt′ /

1. A silvery-white, hard, brittle metallic element that occurs widely in metal ores. It is used to make magnetic alloys, heat-resistant alloys, and blue pigment for ceramics and glass. Atomic number 27; atomic weight 58.9332; melting point 1,495°C; boiling point 2,900°C; specific gravity 8.9; valence 2, 3.

2. See Periodic Table

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Etymology

Origin of cobalt

1675–85; < German Kobalt, variant of Kobold kobold

Compare meaning

How does cobalt compare to similar and commonly confused words? Explore the most common comparisons:

• cobalt vs. royal blue

Explanation

Cobalt is a silvery-gray metal. It's also the name of a deep blue pigment that's made from cobalt. Cobalt, mined from the earth's crust along with copper and nickel, has a shiny appearance with a slightly bluish tint. Chemically combining cobalt with aluminum oxide results in the blue pigment that's been familiar to artists for centuries. Cobalt blue is the blue in very old Chinese blue-and-white porcelain, and it features in paintings by Monet and van Gogh. Cobalt is from the German kobold, "household goblin," a nickname miners gave arsenic-laced ore that made them sick.

Example Sentences

"The observation of multiple symmetry-protected nodal lines in a simple elemental ferromagnet is therefore highly unexpected and establishes cobalt as a model system for studying the interplay between topology and magnetism."

From Science Daily • Jun. 5, 2026

For decades, cobalt has been considered one of the best understood magnetic metals.

From Science Daily • Jun. 5, 2026

The Canadian nickel and cobalt miner, which has ventures that tie it to Cuba, said it has reached a non-binding agreement to sell warrants for shares to Gillon.

From The Wall Street Journal • May 20, 2026

Last December, the US and DR Congo agreed a partnership to increase access to the region's vast deposits of minerals such as cobalt, coltan and copper.

From BBC • May 1, 2026

Shadows bloomed across the walls and multiplied in the stairwells, and as the light died it got bluer, painting everything around me a deep-sea cobalt.

From "Hollow City" by Ransom Riggs

Related Words

• blue-green