Definition of cobalt in English:



mass noun
  • 1The chemical element of atomic number 27, a hard silvery-white magnetic metal.

    • ‘They blended and heated plutonium with gallium and cobalt and then slowly cooled the molten mixture.’
    • ‘This packing arrangement is also observed for many metals, including rubidium, osmium, cobalt, zinc, and cadmium.’
    • ‘Besides gold and diamonds, the area is rich in copper, uranium, palladium and cobalt, as well as coltan ore.’
    • ‘The slow growth rate is thought to enhance the absorption of heavy metals like copper and cobalt from sea water.’
    • ‘We are already exporting gold and we have substantial resources of silver, uranium, nickel and cobalt, the deposits of which need further investigation.’
    1. 1.1
      as modifier ‘a cobalt sky’
      short for cobalt blue
      • ‘It was of dark cobalt, running to purple, and had golden thread work all along the hem and sleeves.’
      • ‘What snatches of blue sky she could see were deepening from azure to cobalt and she thought she saw the first star twinkling already.’
      • ‘Side plates at each place setting are coloured a brilliant turquoise or patterned in cobalt or shaped like river boats.’
      • ‘I got out my sketch book and showed him some of the paintings I'd done of lizard head spires piercing skies of cobalt and turpentine.’
      • ‘He left a tip and walked outside to his cobalt truck, driving away only a few moments later.’
      • ‘His stormy cobalt eyes glanced down at her and he sighed again.’
      • ‘On a walk through the five-acre garden you encounter great bushes of Blue Bonnet, whose huge flower heads vary from powder blue to cobalt.’
      • ‘This past week in the forest park, the fiery foliage set against cobalt skies was a sight to behold.’
      • ‘He lifted up his cobalt eyes to his friend for only a split second and then glanced back down.’
      • ‘His gaze caught mine and for a second his cobalt eyes were a mirror for the sun.’
      • ‘He muttered something in angry fluent French, as he tilted his head back and looked up at the star-dusted cobalt sky.’
      • ‘The softly tailored look is also very much in this season with glowing colours such as cobalt and rich greens coupled with subtly shaded creams and browns.’
      • ‘And then came the third line, a collection in shades of aquamarine, cobalt, ethereal blue, sky blue, and dream blue.’
      • ‘It was February with cobalt skies, snappy air, and a fresh blanket of snow.’
      • ‘The cloudless sky was the color of cobalt, so blue he felt he could breathe it in and out and become a part of it.’
      • ‘The purple on his surcoat made his striking cobalt eyes seem deep violet.’
      • ‘Other houses' bathrooms are characterised by bright cobalt blues or pearl whites.’
      • ‘Above, the serrated edge of the granite ridge cuts through the cobalt sky.’
      • ‘Not only were his eyes lacking their normal cobalt hue and his pupils disturbingly restricted but now his eyes were blood shot as well.’
      • ‘He took her hand and kissed it, his cobalt eyes twinkling.’

Cobalt is chiefly obtained as a by-product from nickel and copper ores. It is a transition metal similar in many respects to nickel and is mainly used as a component of magnetic alloys and those designed for use at high temperatures


Late 17th century: from German Kobalt ‘imp, demon’ (because the presence of cobalt-bearing ore made it more difficult to extract silver, and miners believed that it was harmful to the silver ore with which it occurred).