Platinum is a natural white precious metal. The annual output of platinum is only one twentieth of that of gold, and it takes five months to extract one ounce of platinum from 10 ton platinum ore. Domestic platinum jewelry usually contains 90% pure platinum and is marked with "Pt900". Platinum has a natural white luster and will not fade after long-term wear. The hardness of platinum makes it the best friend of diamonds. And white gold is gold with some alloys, which appears white. It only contains 75% gold at most. White gold cannot be marked with Pt mark, only gold and its purity can be marked according to its purity. For example, 18K platinum can only be stamped with "18K" and "G750". In the international precious metal market, the price of platinum far exceeds that of gold, which is the highest among all precious metals. In addition, some white jewelry may be made of silver or coated with white metal, which may show its original appearance after a long time. Although platinum is sometimes commonly known as platinum, it should be called "platinum" in a strict sense. Platinum in platinum refers to the chemical element platinum. Therefore, the purity, rarity, durability and natural white luster of platinum are incomparable to platinum.
Therefore, in fact, some jewelry marked "platinum" on the market is not platinum jewelry, so it is very important to look at the imprint on jewelry when choosing.
■ Platinum certification
(1) visual inspection method: marking: each piece of jewelry should be engraved with the chemical composition seal, such as (pt 900) and (PT 750). All stamps that begin with "PT" are platinum ornaments: platinum is tin white, that is, white with gray and bright luster.
(2) Instrument detection: Hardness test: the hardness of platinum is 4-4.5 degrees, which is harder than gold and silver. It is scratched with a knife or glass, but it will not be scratched by nails. Density measurement: Platinum is extremely dense and feels heavy when weighed by hand. The density measured by hydrostatic pressure method should be 2 1.43g/cm. The melting point of platinum is as high as 178. Acid test when the color is unchanged: platinum is chemically stable and insoluble in ordinary acids. Draw platinum on the touchstone, drop hydrochloric acid, and try with hydrogen peroxide under the condition of unchanged wear marks: take a little platinum powder and put it into the hydrogen peroxide bottle, and hydrogen peroxide will immediately produce bubbles. After the reaction, platinum can still be used without any damage.
■ Seven characteristics of platinum
Platinum has always been regarded as a precious metal because of its unique characteristics. In recent years, the International Platinum Association has strongly advocated it, making it more and more important in the wedding ring.
Platinum was widely used in ancient Egypt 3000 years ago. Archaeologists once found that the coffin of an Egyptian priestess was decorated with hieroglyphics made of platinum, which remained perfect for a long time without losing its original luster, fully proving the durability and stability of platinum. Platinum didn't start to glow until the first diamond was dug up in Kimberly Mine in South Africa.
This year, the Italian Platinum Association launched a series of new wedding rings, and put forward seven characteristics of platinum, indicating that platinum is the best choice to become a precious metal.
1. Maximum purity.
Platinum alloy contains 95% pure platinum, and 18K gold contains 75% gold. The purity of a platinum jewelry is higher than that of gold jewelry.
2. The rarest
The world produces platinum 140 tons every year, while the annual output of gold is 3300 tons.
Only skilled craftsmen can make it. The melting point of platinum is higher than that of gold, so the technical requirements for workers are more skilled.
Step 4 be the most stable
Platinum is the metal with the strongest acid resistance, alkali resistance and high temperature resistance, and will not fade or change color. Platinum rings generally don't change.
Form.
5. Good gloss and ductility
Platinum has a natural white color, which will not affect the color of gemstones, but also make gemstones glow "fire". Its good ductility also makes it suitable for processing.
6. Do not cause allergic reaction to the wearer.
7. Valuable and excellent.
■ Common identification methods of platinum
1. color Zephyr: pure platinum is white with bright luster, platinum is beige, and silver is white. Can be distinguished from the surface color.
2. Hand balance method: the density of platinum reaches 265,438+0.45. Through the balance test of the same volume of materials, platinum has a heavy feeling, which is heavier than gold (19.36), K- platinum and silver (10.45).
3. Melting method: The melting point of platinum reaches 1773oC, which is much higher than that of K platinum and silver. General welding guns can't melt platinum, so they can identify the authenticity. And that color of platinum doe not change after cool.
4, marking method: platinum jewelry has a standard imprint. Internationally expressed by PT or PT. For example, the purity of PT950 platinum is 950%.
5. Natural gas method: put jewelry on the twisted gas stove mouth for a few minutes. If the jewelry turns red and heats up to light the gas stove, it is platinum products. This is because platinum can be used as a catalyst to promote the oxidation and heat release of gas and air, and make platinum turn red, thus igniting the gas.
6. Spot measurement method: A Put mercury on platinum, platinum will not be polluted, and gold and silver will be polluted by combining with mercury. B. Put some powder in the hydrogen peroxide bottle with a file at the edge or middle depression of platinum jewelry. Platinum can be used as a catalyst to promote the decomposition of hydrogen peroxide and release oxygen to churn up and down.
■ Look at the logo platinum.
Platinum jewelry usually expresses the texture of jewelry with a few thousandths of platinum, which is also one of the basis for jewelry pricing. Common labels are as follows:
Foot platinum: the platinum content is not less than 990, and it is marked with "foot platinum" or "Pt990".
950 Platinum: The platinum content is not less than 950, and it is marked with "Platinum 950" or "Pt950".
900 Platinum: The platinum content is not less than 900, and it is marked with "Platinum 900" or "Pt900".
The hardness of pure platinum is small, so in order to increase the hardness, a certain proportion of precious metals such as palladium, rhodium and iridium must be added. Pt950 contains 5% palladium, rhodium and iridium, and its hardness is still relatively low, so it is generally used for plain platinum jewelry. Pt900 contains 10% palladium, rhodium and iridium, and its hardness is just suitable for inlaying ornaments. At present, most platinum ring holders are made of Pt900, but a few manufacturers use Pt950 to make ring holders.
Because metals such as palladium, rhodium and iridium are rarer and more expensive than platinum, the price of Pt900 is correspondingly higher than that of Pt950. However, many consumers have formed a habit of understanding gold in the past: the higher the purity of gold, the more valuable it is, and it is applied to the relationship between the quality and price of platinum. So some merchants take advantage of this, deliberately marking the price of Pt950 higher than Pt900, misleading consumers to buy, so as to obtain income, which is bound to be suspected of fraud.