Basic knowledge of precious metals gold silver platinum diamonds

Precious metal jewelry refers to jewelry with precious metals gold, silver and platinum as the main components. The world's gold production is mostly in Russia, South Africa, the United States and Canada. Platinum is mainly produced in Canada, followed by Russia and Africa. China's four major gold producing areas are Jiaodong, West Henan, Heilongjiang and Kuangchuan triangle.

1. Gold

Gold: The density of gold is 19.32g / cm3, the hardness is low, and the hardness of Mohs 2.5 is similar to that of human nails. Gold has high toughness, good ductility, and good thermal conductivity and electrical conductivity. Gold has the metallic luster of gold **, and its luster is brilliant and pleasing to the eye. Disadvantages: low hardness and easy to wear. Thousands of gold ornaments: Thousands of gold with a gold content score of not less than 999. The imprint on the jewelry is "thousand gold" and "999 gold". Thousands of gold jewelry is the highest value hit.

Pure gold decoration mouth: the content of thousand parts is not less than 990, which is called pure gold, and the marks on the jewelry are "full gold" and "990 gold".

K gold: In order to overcome the shortcomings of pure gold jewelry, such as poor hardness, single color, easy to wear, and small patterns, gold alloy jewelry was developed: K gold jewelry is characterized by less gold consumption and low cost, and can be made into various colors and is not easy Deformation and wear.

Common K gold purity range table ☆ is common

Colored K gold: generally ** K gold, white K gold, red K gold.

Most of the colored K gold jewelry is colored 18K gold. In addition to 750 ‰ gold, different proportions of other ingredients in the 18K gold will make the K gold appear in different colors, ** K gold (silver copper in the formula, etc.), red K gold ( The copper point in the impurities of 250 ‰ is more than 2/3 or all of it is copper), white K gold (with silver in the formula)

Second, silver

Silver: The density of silver is 10.5g / cm3, the hardness is Mohs 2.7, silver has good ductility, second only to gold, has good thermal conductivity, electrical conductivity, silver has white and pleasing metallic luster, silver in jewelry has:

Foot silver: Foot silver with a silver content of not less than 990, which is marked as "foot silver".

925 Silver: 925 silver with a silver content of not less than 925 is called "Silver 925" or "S925". Because silver is too soft and easily deformed, less jewelry made of pure silver is used. The majority of silver products on the market are 925 silver.

3. Platinum

Platinum: The density of platinum is 21.45g / cm3 and the hardness is 4.3 Mohs. Platinum has silver-white metallic luster, bright color, good electrical conductivity and thermal conductivity. Platinum has good ductility and malleability, which is close to silver and gold.

Platinum in jewelry is:

Foot platinum (foot platinum)-the one with a platinum content of not less than 990 is called foot platinum, and the mark is "foot platinum".

950 platinum-the platinum content of not less than 950 is called 950 platinum, the mark is "platinum 950" or "Pt950".

900 platinum (900 platinum)-900 platinum with a platinum content of not less than 900 is marked as "platinum 900" or "Pt900".

International standards stipulate that the commonly used purity is 850, 900 and 950.

Method for testing precious metals:

Weighing method in still water: using Ajijud's law, use the balance light to weigh the weight of the test object in the air, and then weigh the weight of the test object in the liquid, using the formula: weight of object in air / weight of object in air Weight-the weight of the object in the liquid × the density value of the liquid at the test temperature to obtain the density of the article. (This method can be gold, silver, platinum)

Touchstone method: The touchstone is a smooth and long rectangular block made of a hard carbon black siliceous siltstone.

Grind a golden path on the touchstone to be tested, and add water dropwise to the golden path of the touchstone, depending on the dissolution rate. If it dissolves quickly, the gold color is lower, and if it is slow, the color is high. Another method is to add nitric acid dropwise, and determine the amount of silver in gold based on how quickly it dissolves. Dropping hydrochloric acid can determine how much copper is contained.

Fluorescence spectrometer test: X-ray detector with certain energy resolution is used to detect various energy characteristic X-rays emitted by the sample at the same time, the output signal amplitude of the detector is proportional to the received X-ray energy, and the energy spectrometer is used to analyze the detection The energy size and intensity of the output signal of the device are used to quantify and qualitatively analyze the sample.

4. Diamond

1. Basic identification of diamonds:

Diamond is a high-quality crystal formed by element C under high temperature pressure.

The Mohs hardness of diamond is 10, which is the hardest mineral in nature.

The refractive index of diamond is 2.417, which is a high-refractive-index crystal with a dispersion of 0.044, which has a more obvious dispersion effect. Due to the high refractive index of the diamond, the shiny surface of the diamond has a typical diamond luster, and the thermal conductivity of the diamond is the highest among all minerals (so use thermal conductivity identification as the main method).

The identification of diamonds can be based on the difference between the physical and chemical properties, processing characteristics and optical effects of diamonds and other similar gemstones. The identification method is to observe and identify the closed eye and 10 × magnifying glass, and then use other methods to identify.

To the naked eye and under 10 × magnifying glass:

(1) Gloss: Diamond has a typical diamond luster;

(2) Color: Most diamonds are colorless and light **, light brown, few colored diamonds, **, blue, pink.

(3) Dispersion: The diamond has a more obvious brilliance, but it is too brilliant.

(4) Processing characteristics: The diamond has extremely high hardness and its unique technology, so that it has the characteristics of smooth surface, straight edges and sharp corners.

Other methods:

(1) Identify with the high thermal conductivity of diamonds; test with a thermal conductivity meter.

(2) Use the relative density of diamonds for identification (this only applies to loose diamonds).

(3) Identify the diamond's lipophilicity; use an oil-based pen to draw a line on the diamond with continuous and uniform thickness

analysis:

Zircon: Due to the low hardness, the Hu ridge lines are often worn, and due to the high birefringence, magnified inspection shows that the facets are double shadowed.

Synthetic cubic zirconia: usually with a shell-shaped fracture at the bottom tip, solitary waist and strong luster.

Lead glass: The ridgeline is seriously worn, and bubbles can be seen through enlarged inspection.

Synthetic silicon carbide: This is the species with the closest parameters to the diamond. Due to the high refractive index, the double shadow line is visible in the part.

Two bottom tips can be seen, and the filamentous cell body can be seen through magnification.

Diamond: Because of its high hardness, the ridges are straight, with sharp angles, and have a sand-like waist with whiskers. Because of its high refractive index, it has a strong luster and has a unique diamond luster.

2. Valuation of diamonds

Factors considered in diamond valuation 4C grading: color, clarity, cut, quality.

A. Color (China Classification)

Qualitative standards

Extreme White 100D

Extreme White 99E

Tebai 98F

Tebai 97G

White 96H

Yellowish white 95-94I－J

Yellow and white 93-92K-L

Yellowish yellow 91-90M-N

Because there are few near-colorless diamonds, color is an important factor in determining value

B, clarity

Diamond clarity is the degree of pure and flawless diamonds. Use 10 × magnifying glass to observe the degree of diamond flaws (the smaller the content, the rarer it is).

LC day flaw level is not visible at 10 ×

VVS1.2 grade 10 × It is difficult to see that there are very small defects (point-like inclusions) close to 5 microns

It is difficult to see small flaws under VS1.2 level 10 ×

SI1.2 level 10 × is easy to see defects

P level 1.2.3 Visible to the inner eye

C. Cutting

The cut diamond is made of: bright light-perfect combination of refractive index and fire light-dispersion

Flash-Facets

D. Weight

The diamond jewelry can be used to set the diameter (average diameter) of the diamond as far as possible. Use the formula: use a round diamond (carat) = φ2 × H × 0.0061

φ is the average diameter of diamond (mm)

Another can be based on the mark on the support.

Combining the above four points can provide a comprehensive and detailed assessment of diamonds (in addition to the market price) 3. Diamond weight representation

Note: Diamond weight is expressed in grams (ct)

1ct = 0.2g 1ct = 100 centimeters waist diameter: 1ct = 6.5mm 1.5ct = 7.4mm 2ct = 8.18mm

0. 10ct ＝ 3.00mm

0.15 ct = 3.40mm

0.20 ct = 3.80mm

0.25 ct = 4.10mm

0.30 ct = 4.35mm

0.35 ct = 4.58mm

0.40 ct = 4.78mm

0.50 ct = 5.10mm

4. Other common sense of diamonds

A. Top 5 diamond producers in the world: Australia, North Il (Africa), Botswana (Africa), South Africa, Russia

China: Liaoning

B. The main cutting centers in the world: Belgium, India, Israel, the United States

C. Main materials of diamond inlay: Pt900, 18K, 14K