My X-Wifes Head

Corundum (crystalline aluminum oxide) is second to diamond in hardness.

There is at least one mineral that has a hardness of 9.25 to 9.5 on Mohs Scale. That is the mineral Moissanite. It is not a very common mineral. It is known primarily from meteorites and certain very unusual igneous rocks. I don't know if there is anything harder (other than diamond, of course). However, if there is, then it is not a common mineral. http://webmineral.com/data/Moissanite.shtml http://mineral.galleries.com/minerals/elements/moissani/moissani.htm http://webmineral.com/determin/metallic_minerals_by_hardness.shtml

The Rock!!

Im a geologist at Yale University. It's a well known fact that pumice is the hardest rock found, even harder than diamonds. It can withstand the pressure of a 10 ton hammer.

Aggregated diamond nanorods are actually slightly harder than the typical diamond

1) "Indentation hardness tests are used to determine the hardness of a material to deformation. Several such tests exist, wherein the examined material is indented until an impression is formed; these tests can be performed on a macroscopic or microscopic scale. For measuring hardness of very small samples nanoindentation is used. When testing metals, indentation hardness correlates linearly with tensile strength. This important relation permits economically important nondestructive testing of bulk metal deliveries with lightweight, even portable equipment, such as hand-held Rockwell hardness testers." Source and further information: http://en.wikipedia.org/wiki/Indentation_hardness 2) "Lonsdaleite (named in honour of Kathleen Lonsdale), also called Hexagonal diamond in reference to the crystal structure, is an allotrope of carbon with a hexagonal lattice. In nature, it forms from graphite present in meteorites upon their impact to Earth. The great heat and stress of the impact transforms the graphite into diamond, but retains graphite's hexagonal crystal lattice. Lonsdaleite was first identified from the Canyon Diablo meteorite, where it occurs as microscopic crystals associated with diamond. It was first discovered in nature in 1967. Hexagonal diamond has also been synthesized in the lab in 1966 or earlier (published in 1967) by compressing and heating graphite either in a static press or using explosives. It has also been produced by Chemical vapor deposition. It is translucent brownish-yellow in color and has an index of refraction from 2.40 to 2.41, a specific gravity from 3.2 to 3.3, and a Mohs hardness of 7–8. The Mohs hardness of diamond is 10; the lower hardness of lonsdaleite is chiefly attributed to impurities and imperfections in the naturally occurring material, and a pure sample could be 58% harder than diamond." "Lonsdaleite might be 58% harder than diamond. Simulations suggest that by applying very high indentation loads to lonsdaleite the mineral should react by increasing its hardness by as much as 78%. The resulting material is calculated to resist indentation pressures of 152 GPa, much higher than diamond, which under the same conditions will break at 97 GPa." Source and further information: http://en.wikipedia.org/wiki/Lonsdaleite Further information: http://www.physorg.com/news153658987.html 3) "What is the hardest rock on Earth? Well, the hardest mineral on earth is a diamond. For rocks, which are made up of one or more minerals, the hardest are those which contain quartz. There is no single "hardest rock" but some of the rocks that would be very hard and strong and well-cemented quartz sandstones (a sedimentary rock), quartzite (a metamorphic rock formed from quartz sandstone) and granites or rhyolites (both igneous rocks with a lot of quartz)." Source and further information: http://www.madsci.org/posts/archives/1996-12/844972915.Es.r.html "The red catlinite from the Pipestone quarries is the second softest rock in the world, and it lies under Sioux quartzite, the second hardest rock in the world." Source and further information: http://en.wikipedia.org/wiki/Catlinite Further information: http://en.wikipedia.org/wiki/Sioux_Quartzite