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A cabochon (/ ˈ k æ b u ʃ ɒ n /; from Middle French caboche 'head') is a gemstone that has been shaped and polished, as opposed to faceted. The resulting form is usually a convex (rounded) obverse with a flat reverse. [1] Cabochon was the default method of preparing gemstones before gemstone cutting developed. [2]
Toggle the table of contents. Hardnesses of the elements (data page) 10 languages. ... Mohs hardness of materials (data page) Vickers hardness test; Brinell scale
Just as the angle of the sides of a cabochon creates the pressure to hold the stone in place, so there is an overlying principle in setting faceted stones. If one looks at a side view of a round diamond, for example, one will see that there is an outer edge, called the girdle, and the top angles up from there, and the bottom angles down from there.
A bowenite cabochon featured as part of the "Our Mineral Heritage Brooch", was presented to U.S. First Lady Mrs. Lady Bird Johnson in 1967. Williamsite is an American local varietal name for antigorite that is oil-green with black crystals of chromite or magnetite often included. Somewhat resembling fine jade, williamsite is cut into cabochons ...
Mohs scale hardness: 7.5–8.0: Luster: Vitreous: Streak: White: Diaphaneity: Transparent to opaque: Specific gravity (Depending on the composition) The rare Zn-rich spinel can be as high as 4.40, otherwise it averages from 3.58 to 3.61. Optical properties: Isotropic: Refractive index: 1.719: Pleochroism: Absent: Solubility: None: Other ...
It has a Mohs hardness of six, a Vickers hardness of 7.7 GPa at a load of 0.98 N, [5] and a specific gravity of 3.25 to 3.55. It is transparent to translucent with indices of refraction of n α =1.663–1.699, n β =1.671–1.705, and n γ =1.693–1.728. The optic angle is 58° to 63°.
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 .
A cabochon yellow-green quartz showing the cat's-eye effect. To bring out the chatoyancy effect, gemstones are typically fashioned into a cabochon cut, characterized by a rounded, flat base rather than facets, with the fibrous structures aligned parallel to the base. High-quality specimens display a single, sharply defined band of light that ...
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