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Most metal borides are hard; [41] however, a few stand out among them for their particularly high hardnesses (for example, WB 4, [42] [43] RuB 2, OsB 2 and ReB 2). These metal borides are still metals and not semiconductors or insulators (as indicated by their high electronic density of states at the Fermi Level ); however, the additional ...
Diamond was the hardest known naturally occurring mineral when the scale was designed, and defines the top of the scale, arbitrarily set at 10. The hardness of a material is measured against the scale by finding the hardest material that the given material can scratch, or the softest material that can scratch the given material.
A given sample of metal will contain many grains, with each grain having a fairly consistent array pattern. At an even smaller scale, each grain contains irregularities. There are two types of irregularities at the grain level of the microstructure that are responsible for the hardness of the material.
It was a small slug of adamantium, the toughest and hardest of all metals..." Adamant and the literary form adamantine occur in works such as The Faerie Queene, Paradise Lost, Gulliver's Travels, The Adventures of Tom Sawyer, The Lord of the Rings, [4] and the film Forbidden Planet (as "adamantine steel").
Chromium is the third hardest element after carbon and boron. Its Mohs hardness is 8.5, which means that it can scratch samples of quartz and topaz , but can be scratched by corundum . Chromium is highly resistant to tarnishing , which makes it useful as a metal that preserves its outermost layer from corroding , unlike other metals such as ...
The archaeological period in which bronze was the hardest metal in widespread use is known as the Bronze Age. The beginning of the Bronze Age in western Eurasia and India is conventionally dated to the mid-4th millennium BC (~3500 BC), and to the early 2nd millennium BC in China; [1] elsewhere it gradually spread across regions.
Osmium is a hard, brittle, blue-gray metal, and the densest stable element—about twice as dense as lead. The density of osmium is slightly greater than that of iridium ; the two are so similar (22.587 versus 22.562 g/cm 3 at 20 °C) that each was at one time considered to be the densest element.