Silver. Characteristics, distribution and genesis

Silver (Ag) is a chemical element with atomic number 47 and atomic mass 107.87. There are two stable isotopes in nature: 107Ag and 109Ag in the ratio 51.35:48.65, as well as over 35 radioactive isotopes with mass numbers from 99 to 123. It is a soft white metal with a density of 10,500 kg/m³, melting point of 961.9°C, and boiling point of 2212°C. Silver has high electrical and thermal conductivity, is resistant to oxygen, but reacts with sulfur vapors and halogens.

Silver does not interact with hydrochloric and dilute sulfuric acids but reacts with nitric and concentrated sulfuric acids. Silver is the most common noble metal in nature, with a clarke value for different rocks of 5–7 × 10^-6%. Silver is predominantly found in sulfides, forms independent minerals, and is present in waters and organisms.

In geochemistry, silver is more mobile than gold. In the oxidation zone of sulfide deposits, silver transitions into solution as sulfate or thiosulfate and is redeposited at depth. It closely associates with zinc, lead, copper, iron, and other elements, forming complex silver-bearing deposits.

Silver is included in the list of minerals of national importance approved by the Resolution of the Cabinet of Ministers of Ukraine dated December 12, 1994, No. 827, as ores of precious metals.

The majority of silver is extracted as a by-product during the processing of non-ferrous metal ores (70%), gold-silver deposits (10–15%), and silver ores proper (15–20%). There are over 50 silver minerals known, of which the most important are: native silver, electrum, argentite, pyrargyrite, proustite, freibergite, stephanite, polybasite, argentojarosite, dyscrasite, hessite, and aguilarite.

Industrially important silver-concentrating minerals include high-silver galenas (up to 17% Ag), fahlores (up to 20%), silver sulfides and sulfosalts, native silver, copper sulfides (up to 2% Ag), low-grade gold, chalcopyrite, and tellurides.

Applications and Raw Material Requirements

Silver has been known to humanity since ancient times and was used as early as the 4th millennium BCE as a monetary equivalent in trade and for jewelry making. The oldest silver mines date back to the 3rd millennium BCE in Asia Minor, and silver was mined in the Carpathians as early as the 8th-9th centuries.

The applications of silver and requirements for its raw materials depend on various industrial and technical needs. Below are the main uses of silver and requirements for its purity and quality:

In the jewelry industry, for making jewelry, coins, medals, high-purity silver is used (mainly 925 fineness and higher)
In electronics and electrical engineering, for production of conductors, contacts, soldering, printed circuit boards, pure silver (99.99%) with minimal impurities is required to ensure high electrical conductivity
In medicine, silver is used in medical instruments, antiseptic preparations (argyrol, protargol), and water disinfection. Pure colloidal silver is required for medical preparations and coatings
In the photographic industry, silver is used in light-sensitive materials for photography and cinema
For mirror and tableware manufacturing, high-quality and pure silver is required to ensure smooth coating
In the chemical industry, high-purity silver with certain additives (for optimal chemical activity) is used in catalysts, chemical processes, and as components for specialized alloys

Silver ores are mineral formations containing silver in concentrations that make their industrial development feasible. The main methods of silver extraction and processing include electrolytic refining of polymetallic sulfide ores (Pb, Zn, Cu), gravity concentration, amalgamation, foam separation, flotation, and cyanidation using sorption technologies. Pure silver (99.9%) is obtained through electrolytic refining and remelted into commercial ingots.

Industrial silver content in ores:

Non-ferrous metal ores – minimum 10–100 g/t
Gold-silver ores – 200‑1000 g/t
Silver ores – 900‑2000 g/t

Economic information about silver

Throughout history, humanity has mined about 640,000 tons of silver, of which 550,000 tons are used in jewelry, 40,000 tons in coins and medals, and 45,000 tons in ingots. Silver prices over the last 10 years have been stable at 4–6 dollars per troy ounce.

The main importers of silver ores and concentrates are Japan, Belgium, Luxembourg, and Germany. The main exporters are Mexico, which exports 5,000 tons, Bolivia with over 2,000 tons, and Canada and the USA. Demand for silver has shown a steady growth trend and reached 30,000 tons at the beginning of the 21st century. The difference between production and demand is currently met by recycling waste from photographic and electronic industries.

Global silver resources are estimated at 1,300–1,400 thousand tons, of which confirmed reserves are 600,000 tons. The main silver reserves are concentrated in countries such as Poland (66,000 tons), USA (53,000 tons), Mexico (45,000 tons), Tajikistan (44,000 tons), Canada (42,000 tons), Kazakhstan (29,000 tons), and Australia (25,000 tons).

The world’s leading silver producers in 2000 were Mexico with 2,620 tons, Peru (2,437 tons), USA (2,060 tons), Australia (2,059 tons), as well as China, Chile, Canada, Poland, Kazakhstan, Bolivia, Russia, Sweden, and Indonesia. Global silver production reaches 18–20 thousand tons. Among the leading companies are Mexico’s “Industrials Penoles,” American “Lucky Friday,” and Bolivian “Consur.” In Europe, Poland is the leading silver-producing country, where “KGHM Polska Miedz” operates.

Genetic and geological-industrial types of silver deposits

Silver deposits are divided into silver ore proper and complex silver-bearing deposits. Genetically, they belong to hydrothermal (plutonogenic, volcanogenic, and amagmatogenic), skarn, massive sulfide, and metamorphogenic groups.

Silver ore proper deposits are predominantly hydrothermal, with the main part belonging to volcanogenic-hydrothermal, and a smaller part to plutonogenic and amagmatic types. They form during the final stages of folded areas development and are usually associated with volcanic belts, where they form veins, stockworks, and mineralized zones. The main mass of hydrothermal ore deposits is associated with rhyolites that completed the formation of volcanic rocks.

Among volcanogenic silver deposits, the following geological-industrial types are distinguished:

Tin-silver (Potosi, Chocaya in Bolivia)
Lead-silver (Los Torres in Mexico, San Cristobal in Peru)
Gold-silver (Tonopah, Delamar in USA, Guanajuato in Mexico)
Copper-bismuth-silver (Jáchymov in Czech Republic)

Some silver deposits are not associated with volcanic structures and are localised as veins and zones of mineralisation in terrigenous and terrigenous-carbonate strata of folded areas. They include:

zinc-lead-silver (Lavrion in Greece, Coeur d’Alene in the USA)
cobalt-nickel-silver (Cobalt, Hauganda in Canada, Kongsberg in Norway)

Complex silver deposits account for the bulk of silver production and include the following geological and industrial types

pyrite polymetallic (Brunswick, Faro, Sullivan in Canada, Broken Hill, Mount Isa in Australia, Kosaka in Japan)
skarn polymetallic (Dalnogorskoye in Russia)
stratiform polymetallic in carbonate and terrigenous rocks (Fortitude in Canada, Mississippi deposits in the USA)
copper-porphyry (Panguna in Papua New Guinea, Bingham, Morsici, Butte in the USA, Botija, Petacilla in Panama)
gold-silver (Dukat in Russia, Kumtor in Kyrgyzstan)
copper-pyrite (Noranda, Horne in Canada)
copper sandstones and shales (Mansfeld in Germany, Nchanga in Zambia, Zhairam, Uzunzhal in Kazakhstan).

Silver deposits in Ukraine

The main regions of silver occurrence in Ukraine are Zakarpattia, Donbas and, to a lesser extent, the Ukrainian Shield. Higher concentrations of silver have been found in native copper ores in Volyn and copper sandstones in the Bakhmut Basin.

Ukraine’s total silver resources are estimated at 600 tonnes, but it is important to note that the silver content of Ukraine’s subsoil is not sufficiently explored.

Silver deposits in Transcarpathia are associated with Neogene volcanism and are represented by deposits of silver ores (Kvasivske), polymetallic ores with high silver content, gold-polymetallic and gold-silver ores (Bihanske, Muzhiyivske, Berehivske), which form the Berehivsko-Bihansky ore district. In addition to these deposits, there are numerous polymetallic occurrences with high concentrations of silver and gold.

The Kvasivske deposit is located in the north-eastern part of the Konfertinsky volcanic structure. The ore is represented by cloak-like deposits with silver grades of 60–70 g/t and lenticular bodies with silver grades of 100–120 g/t. The ore also contains pyrite, marcasite, galena, chalcopyrite and others. The ore is suitable for beneficiation using a flotation and cyanidation circuit with a silver recovery of 91–94%.

The Biganske barite-silver-polymetallic deposit is located in the north-west of the Beregovskoye Highlands, about 20 km from the Beregovskoye deposit. It is characterised by a high silver content in the form of argentite, prustite, enargite and other sulphosols. Silver content in barite and barite-polymetallic veins can reach 500‑1000 g/t.

Polymetallic ores of the Berehivske deposit, which contain small amounts of prustite, polybasite, argentite, electrum, and native silver, have a silver content of about 20 g/t.

Muzhiyivske gold-polymetallic deposit is the most explored deposit within the Berehove ore district. The ore contains significant amounts of gold, silver, lead and zinc, with a silver grade of around 20 g/t.

Among the deposits of polymetallic and gold-polymetallic ores in Donbass, the Nagolny ore district (Esaulivske deposit) and Zhuravske deposit are well-known.

The Nagolny ore district is located in the area of the Main Donbas anticline and the Rovenky rolling uplift. The mineralisation is associated with dome-shaped structures and anticline zones. The main ore minerals are sphalerite, galena, pyrite, arsenopyrite, boulangerite, bornonite, tetrahedrite, argentite, and native gold. The mineralisation developed in three stages: gold-pyrite-arsenopyrite, gold-galena-sphalerite and gold-silver-polymetallic. Silver is concentrated mainly in galena and tetrahedrite.

The Esaulivske deposit is located in the north-west of the Nagolny Ridge. The mineralisation is represented by sulphide and quartz-ankerite veins. The average grade is 157 g/t silver, 3.8% lead, 5.8% zinc and 1.1 g/t gold.

The Zhuravske deposit is located in the northern wing of the Orikhovo-Tarasivska anticline. The ore bodies contain silver grades ranging from 35 to 1834 g/t and gold grades up to 8.8 g/t. Silver is present in argentite disseminated in galena and in sulphosols.

Silver mineralisation is also found on the Ukrainian Shield: ferruginous quartzites in the Chortomlyk structure, alkaline rare metal metasomata in the Perzhanska zone, Kocherivska structure, in the Konksky and Orikhovo-Pavlogradsky fault zones and uranium deposits in the Kirovohrad block.

Silver is an important metal due to its unique properties, such as high electrical and thermal conductivity, oxidation resistance and antiseptic qualities. It is widely used in the jewellery industry, electronics, medicine, film and photographic materials, and water treatment. Ukraine’s significant silver deposits, especially in Zakarpattia and Donbas, make it an important resource for the national economy. However, the development of these deposits requires the rational use and preservation of the natural environment.