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  2. Superhard material - Wikipedia

    en.wikipedia.org/wiki/Superhard_material

    In 2001, a diamond-like-structured c-BC 2 N was synthesized at pressures >18 GPa and temperatures >2,200 K by a direct solid-state phase transition of graphite-like (BN) 0.48 C 0.52. The reported Vickers and Knoop hardnesses were intermediate between diamond and c-BN, making the new phase the second hardest known material. [39]

  3. Indentation hardness - Wikipedia

    en.wikipedia.org/wiki/Indentation_hardness

    In 1925, Smith and Sandland of the UK developed an indentation test that employed a square-based pyramidal indenter made from diamond. [11] They chose the pyramidal shape with an angle of 136° between opposite faces in order to obtain hardness numbers that would be as close as possible to Brinell hardness numbers for the specimen.

  4. 'Antiques Roadshow': $30 Ring Turns Out To Be Worth Fortune - AOL

    www.aol.com/entertainment/2014-02-18-antiques...

    What you have is a ring that looks like it's eight to 10 carats from the top, and ... it's a diamond.' The appraiser said the ring dated back to the 1920s or 1930s ... and would be conservatively ...

  5. Vickers hardness test - Wikipedia

    en.wikipedia.org/wiki/Vickers_hardness_test

    The Vickers hardness test was developed in 1921 by Robert L. Smith and George E. Sandland at Vickers Ltd as an alternative to the Brinell method to measure the hardness of materials. [1] The Vickers test is often easier to use than other hardness tests since the required calculations are independent of the size of the indenter, and the indenter ...

  6. Diamond simulant - Wikipedia

    en.wikipedia.org/wiki/Diamond_simulant

    A diamond simulant, diamond imitation or imitation diamond is an object or material with gemological characteristics similar to those of a diamond. Simulants are distinct from synthetic diamonds , which are actual diamonds exhibiting the same material properties as natural diamonds.

  7. Knoop hardness test - Wikipedia

    en.wikipedia.org/wiki/Knoop_hardness_test

    A pyramidal diamond point is pressed into the polished surface of the test material with a known (often 100 g) load, for a specified dwell time, and the resulting indentation is measured using a microscope. The geometry of this indenter is an extended pyramid with the length to width ratio being 7:1 and respective face angles are 172 degrees ...