Unobtainium

Unobtainium, n. A substance having the exact high test properties required for a piece of hardware or other item of use, but not obtainable either because it theoretically cannot exist or because technology is insufficiently advanced to produce it.

[4] For example, during the development of the SR-71 Blackbird spy plane, Lockheed engineers at the "Skunk Works" under Clarence "Kelly" Johnson used unobtainium to refer to titanium.

Unobtainium began to be used among people who are neither science fiction fans nor engineers to denote an object that actually exists, but which is very hard to obtain either because of high price (sometimes referred to as "unaffordium") or limited availability.

[9] The eyewear and fashion wear company Oakley, Inc. also frequently denotes the material used for many of their eyeglass nosepieces and earpieces, which has the unusual property of increasing tackiness and thus grip when wet, as unobtanium.

[10] By 2010, the term had been used in mainstream news reports to describe the commercially useful rare earth elements (particularly terbium, erbium, dysprosium, yttrium, and neodymium), which are essential to the performance of consumer electronics and green technology, but whose projected demand far outstrips their current supply.

[16] Unobtainium was mentioned briefly in David Brin's 1983 book Startide Rising,[17] as a material that could be used in making weapons[18] and comprising 1% of the core of one of the exomoons of the Kthsemenee system.

[22] In the 2009 film Avatar, Unobtanium is the common name of a rare-earth mineral found exclusively on the exomoon Pandora, highly prized (and priced) because of its application as a powerful superconductor material.

A similar conceptual material in alchemy is the philosopher's stone, a mythical substance with the ability to turn lead into gold, or bestow immortality and youth.