Black gold is a noble metal with an unusual color: composition, methods of production and production of exquisite jewelry

Black gold is a metal that has been gaining popularity in recent years. Jewelry of this shade is in demand. Jewelers say that blackened gold is a godsend for jewelry designers. It has a lot of positive qualities and, despite the cost, always finds buyers.

Black gold ring with stones

Black gold: nature of the metal, composition and distinctive properties

Pure gold can only be yellow. All other varieties are alloys or plated with rhodium of the appropriate shade. This means that black gold does not exist in nature; the alloy of the following metals is responsible for the color:

• 75% pure gold;
• 15% cobalt;
• 10% chromium.

During the production process, the finished composition is subjected to oxidation under high temperature. Thus, the finished products become dark. The alloy is an intermetallic, making it difficult to rework or melt.

Gold ring, decorated in black.
Characteristics of black precious metal:

• Strength: such an alloy completely retains the properties of the main component, but is much stronger and more ductile. Wear resistance is ensured by rhodium coating, which protects the product from oxidation and the influence of environmental factors. Black products are less likely to be subject to deformation and external damage.
• Hallmark: The finished black alloy is traditionally 750 hallmark. 585 purity black gold is often offered on the market. This means that the jewelry is made of white or yellow precious metal, and the unusual color is obtained thanks to a special rhodium plating.
• Shades of black. Since black precious metal does not exist in nature, its shade may vary depending on the processing method. The alloy can have shades ranging from light gray to deep black.

Brown gold

Brown gold ring from de Grisogono
Chocolate gold appeared on the jewelry market not so long ago. According to one version, its creator is the famous jeweler Fawaz Gruosi, founder of the de Grisogono brand, who often experiments with shapes, materials and colors of jewelry. The jeweler does not disclose his technology for obtaining this shade.

It is only known that brown gold is obtained by alloying red and pink gold of various samples. Then it is treated thermally and chemically, gradually oxidizing until the coveted brown color appears on its surface. Experts express the opinion that nickel, manganese, iron and copper help achieve this effect.

TOP 3 ways to obtain dark precious metal

Black gold, a metal that is becoming in demand due to its unusual color, can be obtained by jewelers in several ways. All of them differ in a certain level of complexity, production costs and quality of the resulting product.

Real alloy with ligatures

Melting gold with an admixture of cobalt and chromium produces a metal that is then subjected to oxidation at a temperature of 700-950 degrees. It is cobalt that gives the resulting alloy its black color and, in combination with chromium, is responsible for the strength of the material. The final product is difficult to process, which is why its cost is much higher than yellow gold.

This is the only manufacturing method that allows you to get a rich black color that will not change over time.

Ligatures of gold alloys

Rhodium plating of traditional yellow metal

Rhodium plating is the process of coating yellow gold with a layer of rhodium. A special coating is applied to products using electrodes by galvanization. The resulting layer protects the product from external influences, increasing the wear resistance of the jewelry.

The disadvantage of this processing method is that the rhodium gradually begins to wear off, which means it needs to be renewed periodically. In addition, the method does not allow you to predict the shade that the jewelry will receive in the end.

Amorphous Carbon Treatment

You can add a dark tint to your jewelry using amorphous carbon. Carbon coats an ordinary precious metal, changing its color. This processing method is the most difficult. Most often it is used by jewelers in the manufacture of wristwatches.

Gold-bearing coal

First use of oil

Only since the twentieth century has oil become an important mineral. However, the existence of “mountain” or “stone oil” was known even before our era. When oil came to the surface, it was scooped up and used in construction: as a fastening material and as a substance for sealing roofs. Well, most often oil was used to create torches.

In Ancient Egypt, oil was used in embalming, and the ancient Greeks created a flammable mixture (“Greek fire”) based on oil. As a result, we can draw a small conclusion: oil was attractive either for its ability to burn, or as a bonding agent.

Ancient civilizations did not extract oil, but obtained it where it came out on its own. Later, this mineral was mined with rags: they were thrown into a well, taken out and squeezed out. In 347 AD, the Chinese were the first to extract oil using metal-tipped bamboo trunks that were inserted into the ground.

In the 16th-18th centuries, experiments by chemists showed that by performing certain operations with extracted oil, a higher quality product could be obtained, and perhaps even several. But even at the end of the 18th century, extracting oil did not mean being rich. A striking example is the industrialist Pryadunov, who created an oil refinery in 1746 on the Ukhta River. Several decades later it was abandoned. Maybe it was worth waiting a century?

Oil production in a 16th-century engraving

Innovations in the field of creating colored gold

Progress does not stand still; interesting technologies are developed every year to make the life of craftsmen easier. There are relatively new methods for turning yellow gold into black. Each of them has its own characteristics and requires certain investments, which as a result is reflected in the cost.

Nanomethod for creating metal alloys

This technique involves creating an alloy of copper and potassium sulfide. The result is a heavy, naturally black alloy that is processed at 700°C to produce an attractive shine.

In some cases, the cost of products is increased by adding titanium and iron to the composition. Then the products acquire an unusual olive tint.

Laser metal processing

The method involves the use of special technology. The laser beam absorbs the color of the precious metal, changing it to dark. This method requires the use of expensive equipment, special knowledge and skills. The production of such jewelry is a long and labor-intensive process, which means that not every jeweler can use this processing.

Oil rush

In the USA, people bought land and engaged in “artisanal” mining in order to open a deposit and get rich. At this time, the same process is happening in Siberia. At the same time, a unit of measurement in oil production appeared - the barrel.

Barrel is a barrel in English; its volume was 159 liters.

In the United States, by the 1880s, Rockefeller and his Standard Oil company had become the real oil king. In Russia, more and more foreigners invested money in Baku. Among them were the Swedes Nobels. Baku was completely surrounded by oil rigs, and there was smoke all around. “This is a picture of real hell” - this is how Gorky described Baku.

At the end of the 1870s, Dmitry Mendeleev himself came to Baku. His goal was to improve oil production in the region. It was he who proposed creating an oil pipeline, as well as transporting flammable liquids by special ships. Mendeleev predicted that soon the entire economy would depend on oil production.

“It makes no sense to burn oil - it’s like heating a stove with banknotes,” said the great scientist.

He also said this phrase because in Russia there was an idea to heat houses with oil.

Oil Rigs in Los Angeles (1896)

At the end of the 19th century, scientists worked in three directions: how to squeeze the maximum out of extracted oil (that is, isolate and use all the substances), how to transport it, and how to find new deposits (including deep ones). The transport boom of the early 20th century led to increased oil consumption. Ford's slogan “a car for every home” had to be backed up with barrels of produced oil.

Why do I give examples from the history of the USA and Russia? Because these countries were the leaders in oil production in the world at the beginning of the 20th century. But soon a revolution began in Russia and the country briefly lost its leading position.

Soon oil began to be produced in Arab countries, and then in Africa. New ways of extracting it have also appeared: from the bottom of the sea and ocean.

Oil barrels on horse-drawn wagons, Texas, 1915

The use of black gold in jewelry, combination with stones

Black gold, the color of which looks unusual and unique, is often used by jewelers in the jewelry making process. Such jewelry perfectly complements the business style. Dark precious metal looks great in combination with stones:

• diamonds;
• emeralds;
• opal;
• rubies.

At the same time, jewelers rarely inlaid their products with inserts, since the black color can reveal all their flaws. It is for this reason that for many years dark jewelry was decorated exclusively with black diamonds.

The range of unusual metals is becoming diverse. A brutal men's ring, a women's ring, a watch, or bracelets made of black gold looks great. Rings with the engraving save and preserve look unique. Such products belong to minimalism and look great without stones.

Some jewelry houses are experimenting by combining black alloy with platinum and gold of other shades. Such products look attractive, but are also quite expensive. In most cases, the alloy is used to produce jewelry for men, emphasizing the high status of the owner.

Ring black gold with red ruby

How do you get it?

Color can be achieved in three ways:

1. Chromium, cobalt and sulfur are added to the alloy.
2. Covered with a layer of rhodium.
3. Using amorphous carbon.

Chromium and cobalt are present in the alloy in the amount of 25%, so jewelry of this color has a purity of 750. If this is not enough, then the alloy is processed; it undergoes oxidation at high temperatures.

Characteristics of the components of the ligature:

• Cobalt is a silver-colored element with a yellowish or bluish tint. Durable, oxidizes at temperatures above 300 degrees.
• Chrome is a hard element and has a blue or black tint. Amenable to mechanical action.
• Sulfur acts as an additional material; it is capable of creating compounds with carbon and other elements.

By adding these materials to the alloy, the alloy becomes durable, practical and acquires the desired shade.

Earrings made of white and black gold

Jewelry is coated with rhodium, a process called rhodium plating. As a result, a film is formed on the surface of the product, which protects against damage and adds color. Rhodium plating is a complex process; the surface of the metal can be coated not only with rhodium, but also with amorphous carbon.

When rhodium plating, the master can control the process of changing the color of the jewelry.

The product receives a shade from gray to black. Today, laser technology is used to make such jewelry.

Pros and cons of black gold jewelry

The advantages of metal include:

unique appearance;

products made from this alloy are much stronger than those made from other metals;

The alloy is hypoallergenic and cannot cause health problems.

The disadvantages are:

the price of such products can be quite high;

modest assortment - not all jewelry stores are ready to sell such expensive goods;

Scratches, abrasions, chips on the black color become immediately noticeable.

Oil of the 20th century

In the 20th century, oil pipelines became the arteries of state economies. Countries fought wars for access to this mineral, and also organized coups in order not to lose the resource market.

During the Arab-Israeli wars, oil for the first time became more than an economic resource. It has become a political weapon, a method of pressure. So the Arabs raised oil prices for countries supporting Israel. In the 1980s, the rapid fall in oil prices became one of the reasons for the collapse of the USSR.

Safe purchase of real black gold

It is best to buy such unusual jewelry and not regret it at large retail outlets, chains of jewelry stores with a good reputation. When inspecting jewelry, you should examine the mark on the product, passports and certificates.

Of course, the range of online stores is more attractive, but at the same time the risk of overpaying or getting a counterfeit increases. In this case, the jewelry is unlikely to mean or cost much, but getting the money back for it will be problematic.

In the Russian Federation, according to the Law, it is impossible.

Products made from dark alloy are produced in large factories and small jewelry workshops. Most often, those jewelry that are made by hand are valued accordingly. You can buy dark alloy inexpensively in pawn shops or secondhand from those who want to sell their jewelry.

Black gold is durable and wear-resistant

BLACKING GOLD ALLOY ZlSRM 583-80

The specified compositions were tested for:

1) spreadability of black on the surface of gold ZlSrM 583-80;

2) the adhesion strength of the ferrous alloy;

3) porosity of the black coating;

4) color and gloss of the black coating;

5) chemical stability of the ferrous alloy.

Given in table. 2 blackening compositions are resistant to treatment in dilute alkalis (for example, 5-10% aqueous solutions of NaOH and KOH) and acids (for example, 10% aqueous solutions of HCl, H2SO4, HNO3, CH3COOH) for 15 minutes and pass tests for impact (at a load of 0.02 Gm/cm2) and rupture (elongation doubled).

The spreadability of black on the surface of the ZlSrM 583-80 alloy was determined by melting rods of black at the optimal temperature. To measure spreadability, powders of a certain fraction are prepared from the ferrous alloy (residue between sieves No. 02 and 0063).

The spreadability of black on the surface of the ZlSrM 583-80 alloy was determined by melting rods of black at the optimal temperature. To measure spreadability, powders of a certain fraction are prepared from the ferrous alloy (residue between sieves No. 02 and 0063). A 1 g sample of powder is moistened with a solution of a mixture of ammonium chloride and ammonium nitrate and pressed into rods with a diameter of 10 mm using a manual press, then placed on a prepared plate of gold alloy ZlSrM 583-80 and dried in an oven at a temperature of 100-150oC for 2 hours, after which they are placed in a muffle furnace heated to the test temperature. After 1.0-1.5 minutes, when the black melts, the plate is removed from the muffle and after cooling, the diameter (mm) of the spread drop is measured.

The adhesion strength is determined by bending a gold plate with a black pattern at an angle of 90° and returning it to its previous position. The adhesion is considered good if, after bending twice, the black coating remains unchanged. The presence of small cracks and chips at the boundary of the ZlSrM 583-80 alloys and black, visible through a microscope, is allowed.

When testing for tensile strength, a gold plate with a niello pattern is rolled on a roller, as a result of which the ZlSrM 583-80 alloy with niello is elongated. If, with a double elongation at the boundary of the niello - ZlSrM 583-80 alloy, chips and cracks are not detected during visual inspection, the adhesion is considered good.

The porosity of the draft pattern is determined by the number of pores per 1 cm2. A dense black pattern is considered to be one where per 1 cm2 there are no more than four pores with a diameter of 0.1 - 0.2 mm.

The color and gloss of the black alloy are determined visually by comparison with the sample, taking into account that a well-melted black alloy should have a metallic shine after the allowance. The color of the niello should be velvety black.

The chemical stability of the ferrous alloy is tested in aggressive environments. To quantitatively determine the chemical stability of a ferrous alloy, the grain method is used: the change in the weight of the ferrous alloy after treatment in mineral acids [5]. In addition to the grain method, the quality of the niello pattern is determined by first keeping it in solutions of nitric, sulfuric and acetic acids and alkali solutions for 14 minutes. A black coating that has not lost its shine, color, and does not have pores is considered chemically resistant.

One of the most important technological parameters is the firing temperature of the ferrous alloy. To establish the temperature regime for firing niello, gold plates ZlSrM 583-80 were prepared, onto which niello was laid. The plates were dried and fired in a muffle furnace at a fixed temperature. Melting of the black was assessed visually. The optimal firing temperature was determined by the spreadability of the niello, the strength of its adhesion to the gold base, and the degree of porosity of the coating. The results are given in table. 3.

Table 3

Fusibility and spreadability of niello during firing

According to the table. Figure 3 shows that at temperatures above 660°C, complete spreading of the black on the sample is observed.

Tests have shown (Figure) that the spreadability of a drop of black melt increases with increasing temperature. However, the droplet diameter increases relatively little when the temperature increases from 660 to 720oC. This is due to the surface tension of the melt and the wettability of the gold alloy.

Good adhesion of the ferrous alloy ZlSrM 583-80 was achieved due to the introduction of ammonium salts into the composition of the first chloride-nitrate mixture.

When heating a ferrous alloy containing ammonium nitrate and ammonium chloride, the following processes occur on the surface of ZlSrM 583-80 gold:

— chemical reactions;

- mutual diffusion: melt - solid.

Chemical reactions

When heated, a mixture of ammonium nitrate and ammonium chloride is reactive, like a mixture of nitric and hydrochloric acids, therefore, until the ammonium salts are completely decomposed (~700°C), a gold dissolution reaction occurs at the boundary of the molten black - gold alloy ZlSrM 583-80 type Au + 3HNO3 + HCl → HAuCl4 + 3NO2 + 3H2O with subsequent reduction of gold from hydrochloric acid or its ammonium salts. Reduced gold ensures reliable adhesion of the ferrous alloy to the base.

Diffusion

The features of the diffusion process in a solid depend significantly on the defectiveness of the structure of the solid [6].

In the ZlSrM 583-80 alloy, diffusion occurs through interstices and vacancies: elements of the ferrous alloy penetrate from the surface to a depth of 80 microns. To determine the diffusion layer from the surface of the ZlSrM 583-80 alloy, the authors prepared thin sections and examined them using a metallographic microscope.

It has been established that lead is especially active in reactions of this type. If you remove the black alloy from the surface of the ZlSrM 583-80 alloy and dissolve it by heating it in HNO3, a dark, rough trace will remain on the surface. During special heat treatment, swelling occurs in place of the dark spot, which is characteristic in the presence of lead impurities.

In order to confirm the presence of lead impurities in the surface layer of the ZlSrM 583-80 alloy after removal of the black, a spectral analysis was carried out, which showed the presence of traces of lead, however, no such traces were found in the standard sample of the ZlSrM 583-80 alloy. When the black spot is etched with concentrated nitric acid, a clear crystalline structure with obvious traces of insoluble impurities is observed on the surface of the gold alloy.

Based on the studied experimental data, the authors developed a technological process for decorative processing of gold products with a new blackened alloy.

Pricing factors, cost per gram

High cost always indicates the quality of the product. Factors influencing the price of blackened gold:

• production method: the cost of alloy and rhodium plating is significantly different;
• the price set by the Central Bank for 1 gram of yellow gold;
• sample of the components of precious impurities;
• the presence or absence of stones, pearls or other metals in the product;
• method of production of jewelry: handmade products are more expensive;
• costs associated with the production process and delivery of goods to the point of sale.

The average cost of 1 gram of dark gold in Russia is calculated taking into account the rate of 999 fineness and the fineness of ferrous metal as follows:

Registration price of 999 gold according to the Central Bank * share of metal in the alloy

Wedding rings made of black gold
For example, dark gold 750, respectively, on the Russian market will cost:

A bit of geology

The formation of oil is a long process that began tens or even hundreds of millions of years ago. Microorganisms died, fell to the bottom, and were covered with silt. Under special pressure and temperature conditions, a special hydrocarbon mixture was formed.

According to Mikhailovsky, a Russian geologist of the early twentieth century, oil was formed as a result of the breakdown of plant and animal organisms in clay silt, and then ended up in special “collectors” formed as a result of the movement of lithospheric plates.

Oil in Russia

How to choose dark metal jewelry

Since blackened gold does not exist in nature, but is an alloy of human hands, you need to be able to verify its authenticity. The cost of the finished product will depend on the method of obtaining the valuable color. Silver and gold plated with rhodium are valued less than the pure alloy. They also differ in quality and properties. It is worth paying attention to the following details:

• natural alloy is always marked with 750 hallmark: products made of other metals coated with rhodium will have lower hallmarks;
• When metal is coated with rhodium, the dark color can last quite a long time, but products that have been sprayed may have flaws - weak coloring of hard-to-reach places, uneven shade. This becomes especially noticeable on products such as a cross, pendant or earrings.

Before making a purchase, you should check certificates and passports confirming the origin and purity of the metal.

Black gold ring

Purple gold

Violet Gold Bracelet by Lecil Henderson
Violet gold is often called purple or amethyst for its interesting lavender hue. True, it is not used as an independent metal from which jewelry is made. He is the most fragile of all. Therefore, it is used as decorative inserts in jewelry, and it is obtained by mixing gold and aluminum.

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Proper care of dark gold jewelry

The alloy is much stronger than other metals, but even it can look ugly if handled carelessly and without proper care. You can preserve the appearance of an unusual product by following simple recommendations:

• Rafting does not like water: it is better to remove jewelry before visiting the pool or gym.
• It is necessary to limit the contact of jewelry with chemicals.
• To store ferrous metal, you need to purchase a separate case: chains, bracelets and other small items should be stored straightened, avoiding creases.
• You should not leave jewelry in the kitchen or bathroom: high humidity can reduce the natural shine.
• Cleaning of products is carried out only with a weak soap solution. It is allowed to wipe the elements only with soft cloths. The use of brushes can cause scratches and abrasions, which will ruin the appearance.

Reviews

I have been wearing a black gold ring for more than 3 years. Decoration always attracts attention and emphasizes the image. During wear, small abrasions appeared, but they were almost unnoticeable.

Veronica S., Nizhny Novgorod

Anna R., Novosibirsk

I used to buy items made of white or yellow gold, but when I found out about black gold, I was very surprised. The attention was drawn to the elegant earrings, without which it was impossible to leave the store. I bought them, although the cost was much higher than that of analogues made from the usual precious metal.

I really liked the dark and white metal watches. It looks unusual and stylish. But you need to wear it carefully; any damage to the case becomes immediately noticeable. And after constant contact with water, the surface began to shine less.

Sergey Ogorodnikov, Chelyabinsk