Gem grading system and certificate of gem grading in new york jewelry agency;
According to the standards of new york Jewellery Organization, gems are classified according to color, clarity, weight, cutting and treatment.
Emerald grading
Color: Color is an important factor to determine the value of emeralds. The color grades of emeralds from high to low are: rich, bright, deep, medium and soft.
Cleanliness: Cleanliness is one of the main indexes to evaluate emeralds. The purity of emeralds can be divided into flawless (FL/IF), extremely fine impurities (VVS 1/VVS2), extremely fine impurities (VS 1/VS2), fine impurities (SI 1/SI2) and impurities (I1) from high to low.
Weight: In the jewelry industry, such as diamonds, carat is the unit used to measure the weight of precious stones. 1 carat equals 0.2 grams.
Cut: Cut is similar to clarity, and its proportion in emerald value is lower than color. This is different from diamonds: the value of diamonds does not depend much on color, clarity, weight and cutting.
Treatment: The definition of emerald treatment comes from AGTA (American Jewelry Trading Association), which is the most authoritative institution for gem treatment, testing and trading. Common treatment methods include dyeing, filling, diffusion and aromatic asphalt.
Ruby classification
Color: Color is an important factor to determine the value of ruby. Ruby is divided into dove blood red, dark, red, purplish and pink from high to low.
Clarity: Clarity is one of the main indexes to evaluate ruby. The purity of ruby can be divided into flawless (FL/IF), extremely fine impurities (VVS 1/VVS2), extremely fine impurities (VS 1/VS2), fine impurities (SI 1/SI2) and impurities (I1/) from high to low.
Weight: In the jewelry industry, such as diamonds, carat is the unit used to measure the weight of precious stones. 1 carat equals 0.2 grams. A 2-carat ruby is not twice as big as 1 carat ruby, but its price is much higher.
Cut: Cut is similar to clarity, and it accounts for less than color in the value of ruby. This is different from diamonds: the value of diamonds does not depend much on color, clarity, weight and cutting.
Treatment: The definition of ruby treatment comes from AGTA (American Jewelry Trading Association), which is the most authoritative gem treatment, testing and trading institution. Common treatment methods include: heating, unheating, dyeing, filling and diffusion.
Sapphire classification
Color: Color is an important factor in determining the value of sapphire. The colors of sapphires are divided into deep blue, bright blue, sapphire blue, medium blue, sky blue, navy blue and gray blue from high to low.
Clarity: Clarity is one of the main indexes to evaluate sapphire. The clarity of sapphire is divided into flawless (FL/IF), extremely fine impurities (VVS 1/VVS2), extremely fine impurities (VS 1/VS2), fine impurities (SI 1/SI2) and impurities (I1) from high to low.
Weight: In the jewelry industry, such as diamonds, carat is the unit used to measure the weight of precious stones. 1 carat equals 0.2 grams. A 2-carat sapphire is not twice as big as 1 carat ruby, but its price is much higher.
Cut: Cut is similar to clarity, and takes a lower proportion in the value of sapphire than color. This is different from diamonds: the value of diamonds does not depend much on color, clarity, weight and cutting.
Treatment: The definition of sapphire treatment comes from AGTA (American Jewelry Trading Association), which is the most authoritative institution for gem treatment, testing and trading. Common treatment methods include heating, unheating and diffusion.
Classification of tanzanite
Color: the color of tanzanite is divided into two series: blue purple and purple blue. According to the color depth and saturation, it is divided into A, A+, 2A, 2A+, 3A and Block-D from shallow to deep. The higher the color concentration and saturation, the higher the value.
Cutting: The cutting of tanzanite refers to the shape, cutting surface and cutting ratio of tanzanite. Tanzanite with excellent cutting quality is dazzling when the light passes through its perfectly proportioned and strictly symmetrical cutting surface to form the maximum radiation. The better the cutting, the higher the value.
Purity: The purity of tanzanite refers to its natural inclusions and mineral characteristics. According to the cleanliness from good to bad, it is divided into if, vvs, vs, si and p. The better the clarity, the higher the value.
Quality: The heavier the quality, the higher the value.
Tourmaline classification
Color: Color refers to the color of a gem under natural light. It is the key place to evaluate tourmaline. The purer and richer the color, the better the quality. If there is green and black in the gem, it may be that the light color affects the value of the gem. Tourmaline is divided into five grades: dark red, red, medium red, light red and light red. Green tourmaline is divided into five grades: dark green, green, medium green, light green and light green.
Transparency: the brightness of a gem refers to the degree to which it allows visible light to pass through, and is the most important factor to evaluate the quality of a gem. A high-quality tourmaline must be bright at first.
The brightness of tourmaline is generally divided into five grades: bright, sub-transparent, semi-bright, sub-semi-bright and opaque. Take ruby as an example. Only the first and second rubies can be regarded as high-quality gems.
Cutting: Cutting is also very important for tourmaline. Cutting is one of the main factors for tourmaline to have beautiful fire color. The cutting specifications of tourmaline can refer to the specifications of diamonds.
Clarity: Clarity refers to the number of defects contained in tourmaline. Tourmaline has many impurities and ice cracks. The purity of tourmaline is based on the naked eye, which is extremely difficult to see, ugly, visible, easy to see and extremely easy to see, among which the first and second grades are high-quality gems. High purity tourmaline is extremely rare, and high quality tourmaline purity can enhance the value of tourmaline.
Quality: Tourmaline is divided into 1~2 carats, 3~5 carats and 5~ 10 carats, with 5 carats as the order of magnitude, and its value is multiplied in turn. /kloc-Tourmaline over 0/5 carats is the most valuable, and it is the main force of tourmaline collection.
Cat's eye grading
Color: There are many colors of cat's eyes, mainly yellow with other colors, the best color is honey yellow, others are yellow-green, brownish green and brownish yellow.
Eyeliner: Eyeliner should be straight, even and continuous, clear and not turbid, bright and not gloomy.
Weight: For gems, the greater the weight, the more the value increases geometrically, and for cat's eyes, it is no exception.
Xinjiang is the origin of high-quality gemstones. Opals produced in Hami, Xinjiang are white, red, purple-blue, brown-red and chicken oil yellow. It is gelatinous, moist and translucent. Polished products can have the feeling of cat's eye. It is suitable for making rings and accessories, and can be used as exquisite carving materials, which is highly praised by stone players. Among them, the original stone exposed to the ground generally has sun rust, mostly purple colloid or protein color, and the texture is good. Underground opals are generally associated with other veins of rocks, with few reserves, which are easily broken by mechanical mining. The colors are red, purple, chicken oil yellow, black and multicolored. Generally, the surface of Opal collected underground is about 1-2cm, with good texture, mostly colloidal and transparent, with red, purple and blue luster, reaching the gem level, and its Mohs hardness is above 7.5 degrees, and its hardness is higher than agate.