Stibnite

Stibnite is a sulfide minerals with chemical composition is antimony sulfide (Sb2S3). The principal ore of antimony. Lead-gray to silvery gray in color, it often develops a black, iridescent tarnish on exposure to light. It normally occurs as elongated, prismatic crystals that may be bent or twisted. These crystals are often marked by striations parallel to the prism faces. Stibnite typically forms coarse, irregular masses or radiating sprays of needlelike crystals, but it can also be granular or massive. A widespread mineral, stibnite occurs in hydrothermal veins, hot-spring deposits, and replacement deposits that form at low temperatures (up to 400°F/200°C). It is often associated with galena, cinnabar, realgar, orpiment, pyrite, and quartz. It is found in massive aggregates in granite and gneiss rocks. Stibnite is used to manufacture matches, fireworks, and percussion caps for firearms. Powdered stibnite was used in the ancient world as a cosmetic for eyes to make them look larger.

Mineral Group: Forms a series with bismuthinite.

Polymorphism & Series: Dimorphous with metastibnite.

Association: Realgar, orpiment, cinnabar, galena, lead sulfantimonides, pyrite, marcasite, arsenopyrite, cervantite, stibiconite, calcite, ankerite, barite, chalcedonic quartz.

Crystallography: Orthorhombic; dipyramidal. Slender prismatic habit, prism zone vertically striated. Crystals often steeply terminated. Crystals sometimes curved or bent. Often in radiating crystal groups or in bladed forms with prominent cleavage. Massive, coarse to fine granular.

Composition: Antimony trisulfide, Sb2S3. Sb = 71.4 percent, S = 28.6 percent. May carry small amounts of gold, silver, iron, lead, copper

Diagnostic Features: Characterized by its easy fusibility, bladed habit, perfect cleavage in one direction, lead-gray color, and soft black streak.

Stibnite Chemical, Physical and Optical Properties

Stibnite is a mineral composed of antimony sulfide (Sb2S3). It has a distinctive silvery-gray to lead-gray color and is known for its unique crystal structure. Here are some of its chemical, physical, and optical properties:

Chemical Properties:

1. Chemical Formula: Sb2S3
2. Chemical Composition: Stibnite is composed of two elements, antimony (Sb) and sulfur (S). It consists of approximately 71.4% antimony and 28.6% sulfur by weight.

Physical Properties:

1. Crystal System: Stibnite crystallizes in the orthorhombic crystal system, typically forming long, slender prismatic or needle-like crystals.
2. Hardness: Stibnite is relatively soft, with a Mohs hardness of about 2.0, making it susceptible to scratching.
3. Density: The density of stibnite varies depending on its purity and crystal structure, but it generally ranges from 4.5 to 4.7 grams per cubic centimeter (g/cm³).
4. Cleavage: Stibnite exhibits perfect cleavage in one direction, meaning it can be easily split into thin, flexible sheets along certain planes.
5. Fracture: Its fracture is typically uneven or subconchoidal.
6. Luster: Stibnite has a metallic luster, giving it a shiny and reflective appearance.
7. Color: Stibnite is typically silvery-gray to lead-gray in color, and its streak (the color left when it’s scratched on a streak plate) is gray-black.

Optical Properties:

1. Transparency: Stibnite is opaque, meaning it does not allow light to pass through it.
2. Refractive Index: Since stibnite is opaque, it does not have a refractive index as transparent minerals do.
3. Birefringence: Stibnite is non-birefringent, which means it does not split light into two polarized rays as some minerals do.
4. Optical Character: Stibnite is isotropic, meaning it has the same optical properties in all directions.
5. Pleochroism: Stibnite does not exhibit pleochroism, which is the property of some minerals to show different colors when viewed from different angles.

Please note that the physical and optical properties of stibnite can vary somewhat depending on its specific crystal structure and impurities present in the mineral. Additionally, stibnite is known to be toxic due to its antimony content, and caution should be exercised when handling or working with it.

Occurrence and Formation of Stibnite

Stibnite (Sb2S3) is a relatively common mineral that occurs in various geological settings around the world. It forms through a combination of geological processes, and its occurrence can be associated with different types of deposits. Here’s an overview of the occurrence and formation of stibnite:

1. Hydrothermal Deposits:

• The most common geological setting for stibnite is hydrothermal deposits. These deposits form when hot, mineral-rich fluids (usually associated with volcanic or magmatic activity) interact with pre-existing rocks.
• Stibnite often crystallizes from these hydrothermal solutions as they cool and precipitate minerals. The antimony in stibnite commonly originates from magmatic sources.

2. Epithermal Veins:

• Stibnite can be found in epithermal veins, which are low-temperature hydrothermal deposits. Epithermal veins form closer to the Earth’s surface and at lower temperatures than deeper-seated hydrothermal veins.
• Stibnite is sometimes associated with gold and silver deposits in epithermal systems.

3. Sedimentary Environments:

• In some cases, stibnite may be found in sedimentary rocks, particularly in sulfide-rich sedimentary sequences.
• Stibnite can be transported and deposited by fluids in sedimentary basins, forming bedded or disseminated deposits.

4. Volcanogenic Massive Sulfide (VMS) Deposits:

• Stibnite can occur as a minor component in VMS deposits, which are typically associated with submarine volcanic activity and are a source of various metal ores.

5. Mineral Associations:

• Stibnite is often associated with other minerals and ores, including antimony minerals such as antimonite, as well as sulfide minerals like pyrite, galena, and sphalerite.

6. Weathering and Secondary Deposits:

• Stibnite can also form as a result of the weathering of primary stibnite deposits, leading to the formation of secondary deposits. This weathering process can lead to the dispersal of stibnite-rich materials in soils and sediments.

It’s important to note that the specific geological conditions and processes leading to the formation of stibnite can vary widely from one location to another. The presence of stibnite can be indicative of certain geological conditions and may be of interest for mining and exploration purposes, particularly due to its antimony content. Stibnite has various industrial applications, including its use in the production of antimony metal and various antimony compounds.

Mining Sources of Stibnite

Stibnite (Sb2S3) is primarily mined as a source of antimony, which has various industrial applications. Stibnite can be found in different mining sources and geological settings around the world. Here are some notable sources of stibnite mining:

1. China: China is the world’s largest producer of antimony, and a significant portion of the global stibnite production comes from this country. The Xikuangshan Mine in Hunan Province is one of the world’s largest antimony mines, and it has been a major source of stibnite.
2. Tajikistan: Tajikistan is another significant producer of antimony, and the Anzob Mining and Milling Complex is one of the country’s main antimony mining operations. Stibnite is a key ore mineral in this region.
3. Russia: Russia has stibnite deposits in several regions, including the Kamchatka Peninsula and the Far East. The Sarylakh-Surma and Vostok-2 deposits are examples of stibnite-rich deposits in Russia.
4. South Africa: Some stibnite deposits are found in South Africa, and antimony mining has historically occurred in the Waterberg district.
5. United States: Stibnite deposits are present in the United States, primarily in the state of Idaho. The Stibnite Gold Project, located in the Stibnite-Yellow Pine mining district, is a notable example of a stibnite deposit in the U.S.
6. Mexico: Mexico has stibnite deposits in various regions, including the state of San Luis Potosi. The Wadley Mine is one of the known stibnite-producing mines in Mexico.
7. Bolivia: Stibnite deposits can also be found in Bolivia, particularly in the Potosi Department. The country has been a minor producer of antimony from stibnite ores.
8. Australia: Stibnite has been mined in Australia, with notable deposits in New South Wales and Tasmania. However, the production of antimony in Australia has been relatively modest compared to other countries.
9. Other Countries: Stibnite deposits are also present in smaller quantities in countries such as Myanmar, Peru, and Canada.

Stibnite is typically extracted through conventional mining methods, including underground mining and open-pit mining, depending on the depth and nature of the deposit. After extraction, the stibnite ore is processed to recover antimony metal or antimony compounds, which find applications in industries such as flame retardants, batteries, and the manufacturing of alloys.

It’s important to note that the availability and economic viability of stibnite mining can vary over time due to factors like market demand, environmental regulations, and the grade of the deposits. Therefore, the prominence of stibnite mining in a particular region may change over time.

Application and Uses Areas

Stibnite (Sb2S3) and its primary component, antimony (Sb), have several important applications and uses across various industries due to their unique properties. Here are some of the key application areas and uses of stibnite and antimony:

1. Fire Retardants:
   • Antimony compounds, particularly antimony trioxide (Sb2O3), are widely used as flame retardants in plastics, textiles, and other materials. They work by suppressing the spread of flames and reducing the release of toxic gases in the event of a fire.
2. Batteries:
   • Antimony is used in certain types of batteries, such as lead-acid batteries, as an alloying agent to improve the mechanical strength and performance of the battery grids.
3. Alloys:
   • Antimony is alloyed with other metals to create alloys with specific properties. For example, antimonial lead, an alloy of lead and antimony, is used in grid plates for lead-acid batteries.
   • Babbitt metal, which contains antimony, is used for bearings and other applications requiring low friction and wear resistance.
4. Ceramics:
   • Antimony oxide is used in ceramics to improve their opacity and whiteness. It also acts as a fining agent to remove small bubbles and impurities during the firing process.
5. Glass:
   • Antimony compounds are used in the production of certain types of glass, such as opal glass, to create a milky white appearance and increase opacity.
6. Semiconductor Industry:
   • Antimony is used in the semiconductor industry for various purposes, including the production of infrared detectors and diodes.
7. Antimonial Compounds:
   • Antimony compounds find applications in the pharmaceutical industry. For example, antimony potassium tartrate (tartar emetic) was historically used as a medicinal compound, although its use has declined due to toxicity concerns.
8. Military Applications:
   • Antimony is used in certain military applications, such as tracer bullets, where its properties help produce a visible trace in flight.
9. Paints and Pigments:
   • Antimony compounds are used in paints and pigments to provide opacity and durability.
10. Textiles:
    • Antimony compounds are sometimes used as a dye mordant in the textile industry to fix dyes to fabrics.
11. Electronics:
    • Antimony can be used in the production of some electronic components and devices.
12. Agriculture:
    • In the past, antimony compounds were used in agriculture as pesticides and fungicides, but their use has decreased due to environmental concerns.

It’s worth noting that while antimony has valuable industrial applications, it can be toxic in certain forms and concentrations. Therefore, its use and disposal are subject to regulations to ensure safety and minimize environmental impact. Additionally, the importance and demand for antimony and its compounds can vary over time and are influenced by factors such as technological advancements and changes in regulations.

References

• Bonewitz, R. (2012). Rocks and minerals. 2nd ed. London: DK Publishing.
• Handbookofmineralogy.org. (2019). Handbook of Mineralogy. [online] Available at: http://www.handbookofmineralogy.org [Accessed 4 Mar. 2019].
• Mindat.org. (2019). Stibnite: Mineral information, data and localities.. [online]