The difference between "fire" and dispersion

What are the differences between "fire" and dispersion? The following small series will introduce to friends!

Fire color

The so-called "fire color" refers to the effect of monochromatic gemstones appearing under the conditions of precise cutting. A typical example is a diamond, a colorless diamond that presents a colorful shimmering facet under the fine cut, greatly increasing its ornamental value. The production of fire must meet two conditions: first, the gem material must have a sufficiently high "dispersion" value, and secondly the material must follow a certain angle and proportion during processing, which varies from material to material.

The so-called "dispersion" is a gemological term. We know that sunlight consists of seven basic colors, but the combined light is called "white light"; and the dispersion means that white light is decomposed into transparent material. The phenomenon of its composition color. Each gemstone has its dispersion value, which is expressed by the difference in refractive index measured for light in the B-line (red zone 686.7 nm) and G-line (purple zone 430.8 nm) in the solar spectrum.

If the chromatic dispersion value is too small, then the decomposition of light will be extremely inconspicuous, such as crystal ~ anyway it looks like it is colorless, no fire; if the dispersion value is too high ~ such as rutile (dispersion 0.28, the highest in the gem, so it can even produce a strong decomposition of light without cutting, which makes it look too dazzling and unattractive (in fact, rutile is mostly colorless, because its dispersion is too strong, its It seems to have a yellow-brown tone, hence the name); the varieties with obvious and appropriate dispersion values ​​in the gemstones are quite limited, and some of them are covered by their own body color (such as garnet, due to their deep body color). Rocks, etc.) make it difficult to compete with diamonds.

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