Vibranium is a rare, extraterrestrial metallic ore, theorized to have been first deposited on Earth by a meteorite 10,000 years ago, which exists in two forms.
The first, Wakandan Vibranium, is found almost exclusively in the tiny African nation of Wakanda. Wakandan Vibranium, though as yet unknown means, absorbs all vibratory energy in its vicinity, such as sound and kinetic energy, with in itself. The apparent observable vibratory rate of the molecules of the Vibranium itself does not increase when the Vibranium absorbs mechanical energy. The outside vibratory energy is stored within the bonds between the molecules making up the Vibranium. As a result, a chunk of Vibranium, which has absorbed a considerable amount of vibratory energy, would be exceedingly hard to demolish. If enough force were applied to this chunk to smash it the Vibranium would explode, releasing much of the absorbed energy. There are limits to the capacity of Vibranium to absorb vibratory energy, although the exact extent of these limits has not yet been determined. For example, in recent years the oil conglomerate Roxxon discovered that a certain small island in the South Atlantic had a foundation composed of Wakandan Vibranium. Roxxon found it necessary to destroy the island and blew it up with bombs. Unable to absorb the force of the explosion, the Vibranium was destroyed, but it did succeed in entirely absorbing the sound made by the explosion.
It was in the mid 80's that the world learned of the existence Wakandan Vibranium, although its existence has been rumored for decades. In the early 1940's a small amount of Wakandan Vibranium came into the possession of the young, brilliant scientist Dr. Myron MacLain. Dr. MacLain began to develop super-strong metals for the US Government at the beginning of World War II. While experimenting on iron alloys for use as tank armor, he accidentally created the ultra-resilient Vibranium-iron alloy shield used by Captain America. Although he was never able to duplicate the alloy, after several decades of continued experiments, MacLain finally produced the formula for True Adamantium for the US Government.
Sometime later the renegade scientist Ulysses Klaw, who had believed the rumors of Vibranium were true, found the great "sacred mound" of Vibranium in Wakanda. The chieftains, also known as kings, of the Wakandans had guarded the mound for generations as a sacred trust. Klaw failed in his attempt to steal Vibranium from the mound but killed the chieftain T'Chaka. T'Chaka's son T'Challa became the new king of the Wakandans and also adopted the sacred guise of the Black Panther. T'Challa strove to end Wakanda's isolation from the rest of the world. He made the existence of Vibranium known to the outside world and sold small quantities of it to foreigners whom he believed would not turn it to harmful ends. T'Challa used the profits to enrich and modernize his nation.
The other form, Antarctic Vibranium also known as "Anti-Metal", has thus far been found only in the isolated region of Antarctica known as the Savage Land. Whereas Wakandan Vibranium absorbs vibratory energy into its molecular bond; Antarctic Vibranium, through a means that is not yet understood, emanates vibrations which cause the atomic and molecular bonds in nearby solid metals to liquefy. If huge quantities of Antarctic Vibranium were gathered together, at some unknown point the accumulated mass would be so great that the vibrations given off by the entire mass would increase logarithmically as more Vibranium was added. Theoretically, if the enormous mound of Wakandan Vibranium were composed of Antarctic Vibranium instead, the resulting vibrations would therefore liquefy metals throughout Africa, and possibly beyond. A fraction of the sacred mound of Wakandan Vibranium was apparently converted to Antarctic Vibranium by particle bombardment. It is not known what the Wakandans have done with this artificially created Antarctic Vibranium.
Vibranium is not an element, despite various references to it as such. The properties of Vibranium do not qualify it to fill any gaps in the Periodic Table of Elements. Moreover, Vibranium could not be an element with a higher atomic weight than any known elements, since it is not radioactive as the elements with the highest atomic weights are.