Which is the hardest precious stone after diamond?

BRY2K

If you are descending the Moh's scale then the answer would be corundum at #9. The classic scale for hardness was published in 1822 by Frederick Mohs, an Austrian mineralogist who got the basic concept from scratch tests performed routinely by miners. Since Mohs published the scale, it bears his name rather than that of the unknown genius who thought of it. The scale selects 10 minerals as standards, arranging in order of increasing hardness. These are, as most of you probably know: 1 = Talc 2 = Gypsum 3 = Calcite 4 = Fluorite 5 = Apatite (fluorapatite) 6 = Orthoclase 7 = Quartz 8 = Topaz 9 = Corundum 10 = Diamond http://www.gemcutters.org/LDA/hardness.htm It is a mineral, not necessarily a precious stone. Feb 15 09, 1:20 PM

looney_tunes

The ruby is the second-hardest precious stone with a hardness of 9.0 as measured on Mohs scale. (There are many minerals with the same hardness number, and corundum is simply the one selected as the test standard for this hardness.) Of naturally-occurring gemstones, only diamond and moissanite are harder; only diamond is a precious stone. http://hubpages.com/hub/Know-Your-Precious-Stones http://en.wikipedia.org/wiki/Ruby Feb 15 09, 1:35 PM

author

The correct answer is Moissanite. Quote: The structure of moissanite is one of its greatest properties. Similar to the diamond structure, moissanite’s structure gives it great strength, making it useful for testing applications and microelectronics. The crystalline structure is held together with strong covalent bonding that gives moissanite its strength along with other properties that rival diamond.[3] Moissanite has little to no anisotropies occurring with in the crystal structure, thus giving it the ability to withstand high pressures and temperatures.[10] On the Mohs scale of hardness, moissanite is graded at 9.25, second in strength only to diamond. Moissanite is harder than rubies and sapphires which come in at a hardness of 9, and significantly harder than cubic zirconia, which is a brittle material and takes damage relatively easily. http://en.wikipedia.org/wiki/Moissanite Feb 15 09, 3:37 PM

zbeckabee

Just to clarify -- Moissanite should be considered a jewel and not a gemstone: Q: Why do you call it (moissanite) "jewel" rather than a gemstone/stone? A: Terms such as gem/gemstone/stone should be avoided as their use is subject to Federal Trade Commission and Industry regulation to prevent consumer confusion. http://www.4facets.com/moissanite.html http://en.wikipedia.org/wiki/List_of_gemstones Feb 15 09, 4:38 PM

queproblema

Moissanite. Also rarer than diamonds. "On the Mohs scale of hardness, moissanite is graded at 9.25, second in strength only to diamond. Moissanite is harder than rubies and sapphires which come in at a hardness of 9,..." http://en.wikipedia.org/wiki/Moissanite "...ruby is the red variety of the species corundum, while any other color of corundum is considered sapphire." http://en.wikipedia.org/wiki/Gemstone (Remember hi-fi needles? They came in diamond, sapphire, or metal. http://www.west-techservices.com/p5.htm) Feb 15 09, 4:41 PM

star_gazer

This interesting site tells of some new synthetic materials that are harder than diamonds! http://24carat.co.uk/harderthandiamondframe.html Feb 15 09, 5:19 PM

queproblema

The reason moissanite is called a jewel instead of a gem is because it's made, not mined. It's synthetic. Naturally-occurring moissanite is so very rare it cannot be used by the jewelry industry. http://www.moissanite.com/learn_more.cfm#a1 I'm now concluding it doesn't qualify as a "precious stone." http://www.answers.com/topic/gemstone-1 http://geology.about.com/library/bl/blgem-to-min-tables.htm Feb 15 09, 6:18 PM

looney_tunes

According to my earlier link, there are only four true precious stones - diamond, ruby, emerald and sapphire. "All other gemstones are known as semi-precious and should not be called precious, although you'll often see them mistakenly called so." This distinctly narrows the field of choices from which to find an answer to the question posed! Feb 16 09, 1:48 AM