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  2. Jeremejevite - Wikipedia

    en.wikipedia.org/wiki/Jeremejevite

    Jeremejevite is a mineral that shows pleochroic properties, which is an optical phenomenon in which the mineral's color appears to change depending on the angle at which it is viewed. Blue specimens from Namibia show a light cornflower blue to colorless to light yellow pleochroism, while yellow materials show light yellow to colorless pleochroism.

  3. Hardnesses of the elements (data page) - Wikipedia

    en.wikipedia.org/wiki/Hardnesses_of_the_elements...

    Mohs hardness of materials (data page) Vickers hardness test; Brinell scale This page was last edited on ...

  4. Hardness comparison - Wikipedia

    en.wikipedia.org/wiki/Hardness_comparison

    A variety of hardness-testing methods are available, including the Vickers, Brinell, Rockwell, Meyer and Leeb tests. Although it is impossible in many cases to give an exact conversion, it is possible to give an approximate material-specific comparison table for steels .

  5. Taaffeite - Wikipedia

    en.wikipedia.org/wiki/Taaffeite

    Taaffeite (/ ˈ t ɑː f aɪ t /; BeMgAl 4 O 8) is a mineral, named after its discoverer Richard Taaffe (1898–1967) who found the first sample, a cut and polished gem, in October 1945 in a jeweler's shop in Dublin, Ireland.

  6. Gemstone - Wikipedia

    en.wikipedia.org/wiki/Gemstone

    Whether a gemstone is a natural stone or synthetic, the chemical, physical, and optical characteristics are the same: They are composed of the same mineral and are colored by the same trace materials, have the same hardness and density and strength, and show the same color spectrum, refractive index, and birefringence (if any). Lab-created ...

  7. Hardness - Wikipedia

    en.wikipedia.org/wiki/Hardness

    When testing coatings, scratch hardness refers to the force necessary to cut through the film to the substrate. The most common test is Mohs scale, which is used in mineralogy. One tool to make this measurement is the sclerometer. Another tool used to make these tests is the pocket hardness tester. This tool consists of a scale arm with ...

  8. Superhard material - Wikipedia

    en.wikipedia.org/wiki/Superhard_material

    At such low load, the hardness values are also overestimated for other materials, for example it exceeds 100 GPa for c-BN. [4] Other researchers, while having reproduced the high ReB 2 hardness at low load, reported much lower values of 19–17 GPa at a more conventional load of 3–49 N, that makes ReB 2 a hard, but not a superhard material ...

  9. Hardenability - Wikipedia

    en.wikipedia.org/wiki/Hardenability

    The cooling rate will be highest at the end being quenched, and will decrease as distance from the end increases. Subsequent to cooling a flat surface is ground on the test piece and the hardenability is then found by measuring the hardness along the bar. The farther away from the quenched end that the hardness extends, the higher the ...