Red sapphire cut 3
Ruby and sapphire are commonly referred to as red and blue gems. In fact, real rubies and sapphire are gem-quality corundums (corundum is a mineral name). The hardness of red and sapphire is Among all the minerals in nature, it is second only to diamond. Their chemical composition is alumina (Al2O3). It is colorless when pure. It is red when it contains 0.9%-4% chromium. It is blue when it contains iron and titanium. The shape is three-way. Crystalline, the crystal form in nature is often columnar (slightly thin at both ends, slightly thick in the middle) or plate-shaped hexagon, the appearance is more like barrel; color is mainly colorless, red and blue, ruby ​​is mainly deep Fuchsia or orange-red, sapphire is mainly blue or blue-green, and other colors are green, yellow, pink, brown, etc.; hardness is 9; relative density is 3.99-4.0; due to common polycrystalline twin crystal, contact twin, There will be cracking; the whole is transparent to translucent, the gloss shows glass luster to yam diamond, ruby ​​has obvious red fluorescence under UV light, most of sapphire is non-fluorescent; usually red and sapphire can reach 1.762 - 1.778, for red and sapphire containing three sets of aligned fibrous inclusions, a curved facet cut can produce a starlight effect.
Red sapphire
Red sapphire good cuts pay attention to three points:
1. Cut positioning: Because red sapphire is anisotropic, it has pleochroism. When cutting, the table should be strictly perpendicular to the long axis, avoiding the influence of pleochroism, so that the finished product can see the purest and saturated color from the table, which is the correct orientation. Otherwise, it will cause color misregistration and be motley due to pleochroism.
2. Proportion and symmetry: Regardless of the type of cutting used by the gemstone, it must meet the requirements of the standard specification, and the symmetry is better and cannot be skewed. Length, width, and thickness ratios and angles are important and must be met because they are designed based on the refractive index of the gemstone and the principle of total reflection of light. If it is thin, it will leak light, the color is light, and the dispersion effect is also poor. In the jargon, there is no "fire head", which is called "fisheye effect". It looks dull and brilliance. If it is cut too thick, it will change color. Dark, also affects the "fire head."
3. Polishing degree: the quality of polishing will affect the luster of the gem. High-quality polishing gives the gem a stronger glow and shines.
4. Starlight effect: For red and sapphire containing three sets of aligned fibrous inclusions, a curved surface cut can produce a starlight effect. The cutting of such gemstones must not only consider the symmetry and proportion, but also select the direction and position so that the starlight of the finished product is in the middle. If the cutting is not good, the value will be reduced if it is skewed.
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