2。 To evaluate the quality of jadeite, keep in mind the four-character standard of "positive concentration and positive balance"
The color of a good piece of jade must be the first element of evaluation, and the standard of a good color is: positive, strong, clear and even.
Positive: refers to the range of hue, which depends on the ratio of primary color to secondary color, that is to say, it should be pure green and not mixed with other colors. For example, oil blue is often mixed with oil blue, and its value will be reduced.
Thick: refers to the depth of color. As far as emerald green is concerned, the concentration is preferably between 70% and 80%, and 90% is too strong.
Yang: It refers to the lightness of jade color. The lightness of jade is mainly determined by the ratio of green to black or gray. The more green, the brighter the color. The more black or gray, the darker the color. Experts often use an image method to express the bright sunshine of color. For example, boxwood green, parrot green, onion heart green and pepper green all refer to the color of fresh sun. Spinach green, oil green, river green and dark green refer to dull dark green. The fresher the jadeite, the higher its natural value.
Average: refers to the uniformity of jade color distribution. The color distribution of jadeite is generally uneven, so it is not easy to get jadeite with uniform color distribution.
The best color: it should be pure green with a green concentration of 70%-80%, bright sunshine and uniform color distribution. This kind of high-grade jadeite habit is called old pit species by experts.
3。 (1) high-grade gemstone
Refers to those gems whose physical properties, such as color, transparency and hardness (generally Mohs hardness HM is greater than 7), belong to the crown of gems. According to the traditional custom and the law of value, the high-grade gems recognized by the international jewelry industry at present include diamonds, emeralds, rubies, sapphires and emeralds (changed stones and cat's eyes).
(2) low-grade gemstones
Also known as ordinary gemstones, it refers to those beautiful, durable and rare gemstones, but inferior to high-grade gemstones. There are many kinds of precious stones with relatively low value, mainly tourmaline, beryl, garnet, pointed crystal, crystal and so on. Earrings and earrings.
(3) Rare gems
Refers to some newly developed new gem varieties. They often can't be widely circulated in the market because of their low output, and can only appear as gem varieties in gem laboratories or showrooms, and their value depends on the specific conditions of the products. For example, Tafei stone is produced in Sri Lanka and can be beige, lavender, reddish and other colors. The earliest discovered original stone is only 1.4 19Ct. According to statistics, so far only a few Tafei stones can be polished into faceted gems.
4。 * * * Five aspects: the size, nature, quantity, location and color of defects.