How to identify silver ore

1. Native Silver: It usually presents a silver-white metallic luster and can be found in massive, granular, dendritic, or reticulated forms. The surface of native silver ore may exhibit a gray or black oxidation layer due to oxidation.

Native Silver is a naturally occurring silver element mineral, often containing other elements such as gold and mercury. It belongs to the cubic crystal system with a copper-type crystal structure. The form of native silver can be single crystals in cubic and octahedral shapes or aggregates of both, but these are rare. Aggregates are usually dendritic, irregular flaky, granular, and massive. Fresh fractures are silver-white, but the surface is usually gray-black due to oxidation, with a metallic luster. Native silver has a Mohs hardness of 2.5, good ductility, and is a good conductor of electricity and heat, with a specific gravity of about 10.1 to 11.1 grams per cubic centimeter.

Native silver is mainly found in some mesothermal and low-temperature hydrothermal deposits, where it can be distributed in microgranular form in the sulfides of lead-zinc hydrothermal deposits. The enrichment of native silver is often seen in so-called Ni-Co-U-Bi-Ag carbonate vein deposits, associated with cobalt-nickel arsenides, silver sulfide minerals, native bismuth, asphaltum uranium ore, etc. In addition, native silver is often enriched in calcite veins containing organic matter, and its composition often contains mercury. Native silver of exogenic origin is found in the oxidation zone of sulfide deposits, similar to the exogenic origin of native copper. The largest silver nugget in nature was found in 1875 at a depth of 300 meters underground in Freiberg, Saxony, weighing 5000 kilograms. Chile has found a flaky native silver weighing 1420 kilograms.

The identification characteristics of native silver include:

1. It dissolves in nitric acid, has a low melting point, and is easily soluble.

2. If exposed to hydrogen sulfide gas, silver will lose its luster.

3. It is a good conductor of heat and electricity.

4. It is characterized by high reflectivity, homogeneity, low hardness; it is distinguished from native gold and electrum by its reflective color; it is distinguished from native bismuth by its homogeneity.

The important production areas of native silver include Kongsberg in Norway, Freiberg and Schneeberg mining areas in Saxony, Germany, Cobalt and Keeley mining areas in Ontario, Canada, and Great Bear Lake area in British Columbia, etc.

Although native silver is beautiful and has unique physical properties, it is not the main source of silver. The commonly used silver is mainly refined from silver-containing minerals such as argentite (Ag2S). Native silver is not as widely used in industry as refined silver, but its rarity and beauty in nature make it an object of interest for collectors and geologists.

1. Argentite (Argentite, Ag2S): It is a common silver sulfide, usually dark gray or black, with a metallic luster. The surface of argentite may have cracks or layered structures.

Argentite (chemical formula Ag2S) is a sulfide mineral known for its silver content and is one of the important mineral raw materials for silver extraction. The crystal form of argentite is relatively rare, usually appearing as granular, massive, or dendritic aggregates. The name of this mineral comes from the Latin word "Argentum," which means "silver."

The physical properties of argentite include:

- Color: Lead gray, sometimes dark lead gray to iron black.

- Luster: It has a metallic luster.

- Hardness: On the Mohs hardness scale, the hardness of argentite is between 2 and 2.5.

- Specific gravity: Approximately between 7.2 and 7.4 grams per cubic centimeter.

- Cleavage: Incomplete cleavage, parallel to (100) and (110) crystal faces.

- Streak: Gray.

- Transparency: Usually opaque.

- Luminescence: None.

- Fracture: Conchoidal fracture.

Argentite mainly forms in hydrothermal deposits, associated with other silver sulfides, native silver, galena, etc. It forms above 179°C, and when the temperature drops below 179°C, it may transform into acanthite.

The famous production areas of argentite are all over the world, including British Columbia and Ontario in Canada, Cornwall in England, Saxony in Germany, Attica in Greece, Ilimaussaq in Greenland, Guanajusto in Mexico, California in the United States, etc. In China, argentite and acanthite are found in many lead-zinc deposits, usually in the form of microgranules distributed in galena and other sulfide minerals. Silver is mainly extracted from these ores in China. The refining process of argentite can produce silver and silver compounds. Silver, due to its unique physical and chemical properties, has a wide range of applications in industry and technology, including jewelry manufacturing, electronic products, photography, and medicine.

1. Chlorargyrite (Chlorargyrite, AgCl): It is a silver halide, usually white or light gray, with a pearl luster or wax-like luster. Chlorargyrite is easily oxidized in the air, and the surface may turn brown.

Chlorargyrite (chemical formula AgCl) is a halide mineral that mainly contains silver elements and is one of the important ores for silver extraction. Its chemical composition is AgCl, and the crystal belongs to the cubic crystal system. The crystal form of chlorargyrite is usually cubic, but this form is relatively rare; they are usually found in massive or encrusted aggregates. Under long-term exposure to sunlight, the color of chlorargyrite will gradually darken and may eventually turn black. Crystalline chlorargyrite presents a diamond luster, while cryptocrystalline has a wax-like luster. The hardness of chlorargyrite is between 1.5 and 2, with good ductility and a density of about 5.55 grams per cubic centimeter.

Chlorargyrite is mainly found in the oxidation zone of silver deposits, usually preserved under arid climate conditions. It is associated with native silver, cerussite, iodargyrite, atacamite, malachite, yellow potassium jarosite, and iron-manganese oxide minerals. This mineral is formed by the oxidation of silver sulfides and the reaction with infiltrating ground water containing chlorine, so it is a secondary mineral.

The production areas of chlorargyrite are all over the world, including Saxony and the Harz Mountains in Germany, Cornwall in the UK, the Altai Mountains in Russia, Idaho, New Mexico, Arizona, and Nevada in the United States, Atacama, Antofagasta, and Tarapacá in Chile, and New South Wales in Australia. These areas are famous for their crystalline form or large and pure blocks of chlorargyrite. Chlorargyrite is not only of great significance in geology and mineralogy but also economically important because it is one of the main sources of silver.