cobalt (n.)
The metal behind cobalt blue takes its name from a goblin. German miners used Kobold for a troublesome spirit, and the name became attached to ores that frustrated their attempts to extract useful metal.1
In Saxony, miners tried smelting what they believed was silver-bearing ore. When it failed to yield the silver they expected, they blamed goblins for bewitching it. Some cobalt ores also contained arsenic, which could be released as poisonous fumes during processing. The material was dangerous as well as disappointing.12
In the eighteenth century, the Swedish chemist Georg Brandt investigated a similar ore and identified a previously unrecognized metal. The miners’ name was carried over to the element.2
Cobalt compounds give glass and ceramics a deep blue color. The name used for that familiar blue preserves the miners’ much less welcome experience of the ore.1
The potter used cobalt to color the glaze.