Adamant

Adamant, a term now used to express any substance of extraordinary hardness, chiefly a rhetorical or poetical word. The name was attached to a supposed stone or mineral, as to the properties of which vague notions long prevailed. It was identified with the lodestone or magnet, and was often used as synonymous with it by early writers. This confusion ceased with the 17th century, but the word for a long time had a currency among scientific writers as a synonym with diamond. The original of the word is the Gr. adamas, originally an adjective meaning 'invincible,' afterwards used as a name of the hardest metal, and also applied by Theophrastus to the hardest crystalline gem then known—the emery-stone of Naxos. Dr Murray says that the early medical Latin writers (apparently explaining the word from adamare, 'to take a liking to,' 'have an attraction for') took the lapidem adamantem for the lodestone or magnet (an ore of iron, and thus also associated with the ancient metallic sense); and with this confusion the word passed into the modern languages.