Regarding the magnification of a magnifying glass for jewelry, some people think that the larger the magnification, the better, but it is not, because it is more than 10 times in lens manufacturing, and it is difficult to ensure its optical quality and light transmission aperture (the light transmission aperture of a magnifying glass is16 mm ~ 20 mm); Secondly, a magnifying glass with a magnification of more than 10 is difficult to use because of its short focal length. When using 10 times magnifying glass, the distance from the fixture to the top of the lens is about 25 mm, which is the most suitable distance; If you use a magnifying glass of 20 times, the distance between the object and the mirror is only 10 mm, which is inconvenient to observe; Another important reason is that the international observation of colored gems's quality is mostly judged by naked eyes, while the observation of diamond's quality is based on 10 magnification. In view of the above reasons, the jewelry industry observes jewelry with a magnifying glass of 10 times. For example, when looking at rubies, sapphires and emeralds with a magnifying glass of 10, the jewelry bought by the buyer has no cracks, but when the buyer looks at it with a magnifying glass of 20 times, he finds that the jewelry has fine cracks or jade lines, so the seller can think that the jewelry is fine.