Look up adamant in Wiktionary, the free dictionary.
and similar words are used to refer to any especially hard substance, whether composed of diamond, some other gemstone, or some type of metal. Both adamant and diamond derive from the Greek word ἀδάμας, ἀδάμαντος (adamas, adamantos), meaning "untameable". Adamantite and adamantium (a metallic name derived from the Neo-Latin ending -ium) are also common variants.
Adamantine has, throughout ancient history, referred to anything that was made of a very hard material. Virgil describes Tartarus as having a screeching gate protected by columns of solid adamantine (Aeneid book VI). Later, by the Middle Ages, the term came to refer to diamond, as it was the hardest material then known.
It was in the Middle Ages, too, that adamantine hardness and the lodestone's magnetic properties became confused and combined, leading to an alternate definition in which "adamant" means magnet, falsely derived from the Latin adamare, which means to love or be attached to. Another connection was the belief that adamant (the diamond definition) could block the effects of a magnet. This was addressed in chapter III of Pseudodoxia Epidemica, for instance.
Since the word diamond is now used for the hardest gemstone, the increasingly archaic term "adamant" has a mostly poetic or figurative use. In that capacity, the name is frequently used in popular media and fiction to refer to a very hard substance.
In John Milton's epic poem Paradise Lost, adamant or adamantine is mentioned eight times. First in Book 1, Satan is hurled "to bottomless perdition, there to dwell in adamantine chains and penal fire" (lines 47–48). Three times in Book 2 the gates of hell are described as being made of adamantine (lines 436, 646 and 853). In Book 6, Satan "Came towring [sic], armd [sic] in Adamant and Gold" (line 110), his shield is described as "of tenfold adamant" (line 255), and the armor worn by the fallen angels is described as "adamantine" (line 542). Finally in book 10 the metaphorical "Pinns [sic] of Adamant and Chains" (lines 318–319) bind the world to Satan, and thus to sin and death
In the 1956 movie Forbidden Planet, Dr. Morbius describes the Krell towers as being made of "glass and porcelain and adamantine steel."
In Marvel Comics, adamantium (first appearance: Avengers #66, July 1969) is a nearly indestructible metal that coats the skeleton of the superhero Wolverine and makes up the body of the supervillain Ultron.
In the tabletop roleplaying game Dungeons and Dragons, Adamantine is an extremely hard exotic metal. Adamantine weapons can easily deal damage to golems and tough inanimate objects.
In the MMORPG game RuneScape, Adamantite is a durable metal used for armor and weapons.
In the multi-platform game Terraria, Adamantite is a material used to craft several tools and armor.
In the action role-playing game Dragon Age: Inquisition, Adamant Fortress is the name of an ancient Grey Warden keep besieged by the player's forces.