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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.

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

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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

Etymology

Origin of cobalt

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

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Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

After cobalt prices crashed in 2023, Chemaf’s founder put the company up for sale.

From The Wall Street Journal • Mar. 31, 2026

Caught in the middle is American mining company KoBold Metals, which uses AI to scour for copper, lithium, nickel and cobalt.

From The Wall Street Journal • Mar. 28, 2026

China currently dominates the global supply of lithium and cobalt, both of which are needed in batteries.

From Barron's • Mar. 28, 2026

China currently dominates the global supply of lithium and cobalt, both of which are needed in batteries.

From Barron's • Mar. 28, 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

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.