Fluorite (Fluorspar)

Fluorite, also known as fluorspar, is a widely occurring mineral found in various geological settings around the world. It is a colorful and highly valued mineral due to its vibrant fluorescence when exposed to ultraviolet light, which gives it its name. Fluorite has a fascinating range of physical properties and has numerous industrial, scientific, and ornamental applications.

Fluorite, Yaogangxian Mine, Yizhang County, Chenzhou Prefecture, Hunan Province, China
Fluorite Scheelite
Blue Fluorite with Phantom Purple
Fluorite from England. (public display, Carnegie Museum of Natural History, Pittsburgh, Pennsylvania, USA)

An important industrial mineral. Fluorite commonly occurs as vibrant, well-formed crystals. A single crystal may have zones of different colors that follow the contour of the crystal faces. Fluorite crystals are widely found in cubes, while fluorite octahedra which are often twinned are much less common. The mineral can also be massive, granular, or compact. Fluorite occurs in hydrothermal deposits and as an accessory mineral in intermediate intrusive and silica-rich rocks. It is used in the manufacture of high-octane fuels and steel and in the production of hydrofluoric acid. (Bonewitz, 2012)

Name: From the Latin to flow, in allusion to its low melting point.

Cell Data: Space Group: Fm3m. a = 5.4626 Z = 4

Association: Quartz, dolomite, calcite, barite, celestine, sulfides, cassiterite, topaz, wolframite, scheelite, apatite.

Crystallography: Isometric; hexoctahedral. Habit cubic, often in twinned cubes. Other forms are rare, but examples of all the forms of the hexoctahedral class have been observed; the tetrahexahedron and hexoctahedron are characteristic. Usually in crystals or in cleavable masses. Also massive; coarse or fine granular; columnar.

Fluorite Composition: Calcium fluoride, CaF2. Ca = 51.1 percent, F = 48.9 percent.

Diagnostic Features. Determined usually by its cubic crystals and octahedral cleavage; also vitreous luster and usually fine coloring, and by the fact that it can be scratched with a knife.

Contents

• Chemical Properties of Fluorite
• Physical Properties
• Optical Properties
• Formation and Occurrence of Fluorite
• Types and Varieties of Fluorite
• Historical Significance of Fluorite
• Application and Uses Areas of Fluorite
• Locations and Deposits
• References

Chemical Properties of Fluorite

1. Chemical Formula: CaF2 (calcium fluoride)
2. Chemical Composition: Each unit of fluorite consists of one calcium (Ca) atom bonded to two fluorine (F) atoms.
3. Ionic Bonding: Fluorite is held together by ionic bonds, with calcium ions (Ca²⁺) being positively charged and fluoride ions (F⁻) being negatively charged. These ions attract each other, forming a stable crystal lattice.
4. Density: The density of fluorite typically ranges from 3.18 to 3.25 grams per cubic centimeter (g/cm³).
5. Chemical Inertness: Fluorite is chemically inert and does not readily react with most acids or common chemicals.
6. Solubility: While relatively insoluble in water, fluorite can slowly dissolve over time when exposed to acidic groundwater or soil.

These chemical properties are fundamental to fluorite’s composition and behavior in various chemical and geological contexts.

Physical Properties

Optical Properties

Optical Properties of Fluorite : under PPL

Formation and Occurrence of Fluorite

Fluorite, a calcium fluoride mineral with the chemical formula CaF2, forms in a variety of geological settings through both hydrothermal and sedimentary processes. Its occurrence is influenced by the availability of calcium and fluorine ions, as well as specific geological conditions. Here’s an overview of the formation and occurrence of fluorite:

1. Hydrothermal Formation:

• Primary Hydrothermal Deposits: One of the most common ways fluorite is formed is through primary hydrothermal processes. In these settings, hot, mineral-rich fluids (hydrothermal solutions) percolate through cracks and fissures in the Earth’s crust. These fluids carry dissolved calcium and fluorine ions derived from the surrounding rocks. When these solutions cool and react with other minerals, they can precipitate fluorite crystals.
• Associated Minerals: Fluorite often forms alongside other minerals such as quartz, calcite, sulfides (like galena and sphalerite), and sometimes even with other fluorine-bearing minerals like topaz. The presence of these minerals can influence the color and appearance of fluorite crystals.

2. Sedimentary Formation:

• Evaporite Deposits: Fluorite can also be found in sedimentary environments, particularly in evaporite deposits. Evaporite deposits form when saline waters in basins evaporate, leaving behind the dissolved minerals as solid deposits. If these waters contain sufficient calcium and fluorine ions, fluorite can precipitate and accumulate in layers.
• Marine Sediments: Fluorite may also occur in marine sediments, where it forms as a result of the slow accumulation of organic matter and minerals in marine environments.

3. Metamorphic Processes:

• Fluorite can be present in certain metamorphic rocks, although it is not a common constituent. It may form during the metamorphism of sedimentary rocks that contained fluorine-rich minerals or as a result of the alteration of pre-existing fluorite deposits.

4. Igneous Rocks:

• While fluorite is not typically associated with igneous rocks, it can occasionally be found in small quantities in some igneous environments, particularly in granitic intrusions. This is because fluorine can be present in the magma and may crystallize into fluorite under specific conditions.

5. Carbonatites:

• In some rare cases, fluorite is found in carbonatite rocks. Carbonatites are igneous rocks composed primarily of carbonate minerals, and they can contain various rare minerals, including fluorite.

Types and Varieties of Fluorite

Fluorite, also known as fluorspar, exhibits a wide range of colors and variations due to impurities and trace elements. These differences in color and crystal habit have led to the recognition of several types and varieties of fluorite. Here are some of the most well-known types and varieties:

1. Color Varieties:
   • Purple Fluorite: Perhaps the most famous variety, purple fluorite can range from pale lavender to deep violet. It is often associated with quartz and is highly sought after by collectors.
   • Green Fluorite: Green fluorite can vary in shade from pale green to emerald green. It is a common variety and is frequently used in carvings and jewelry.
   • Blue Fluorite: Blue fluorite is less common than some other colors. It can range from light blue to deep azure and is often associated with other minerals like quartz or calcite.
   • Yellow Fluorite: Yellow fluorite ranges from pale yellow to golden hues. It is often found alongside other colorful fluorite varieties.
   • Pink Fluorite: This variety features shades of pink, from soft pastels to more vibrant pinks. It is less common but prized for its beauty.
   • Colorless Fluorite: Some fluorite crystals are entirely colorless, but they often exhibit strong fluorescence when exposed to UV light.
   • Multicolored or Banded Fluorite: Occasionally, fluorite crystals display bands or zones of different colors, creating a striking and visually appealing appearance.
2. Phantom Fluorite: Phantom fluorite crystals have a distinct internal “ghostly” outline or shape within the crystal. This is caused by the growth of the crystal over time, with the interior gradually changing color or clarity.
3. Octahedral Fluorite: Fluorite typically crystallizes in octahedral shapes, which are eight-sided. Specimens with well-defined octahedral crystals are highly valued by collectors.
4. Cubic Fluorite: While most fluorite crystals are octahedral, cubic fluorite is characterized by cube-shaped crystals. These cubes often have sharp edges and can range in size from small to quite large.
5. Cleaved Fluorite: Fluorite has perfect cleavage in four directions, meaning it can be easily split into octahedral fragments. Specimens that display these cleavage planes are often prized for their clarity and symmetry.
6. Yttrium Fluorite: Yttrium-doped fluorite, also known as Yttrian fluorite, is a variety that contains yttrium ions as impurities. This type of fluorite can display enhanced fluorescence and is used in some specialized applications.
7. Other Varieties: In addition to the above, fluorite can also be found in other variations, including rainbow fluorite (exhibiting multiple colors in one specimen), opalescent fluorite (with a milky, opalescent sheen), and more. The naming of fluorite varieties can sometimes be based on their locality or unique characteristics.

It’s important to note that the specific appearance and colors of fluorite can vary greatly depending on its source and the impurities present in its formation. Fluorite specimens are highly prized by mineral collectors for their diverse range of colors and crystal habits, and they are often used in jewelry, carvings, and decorative pieces due to their beauty and aesthetic appeal.

Historical Significance of Fluorite

Fluorite, also known as fluorspar, has historical significance in various cultural, industrial, and scientific contexts. Here are some of the key aspects of its historical importance:

1. Industrial Use in Metallurgy: Fluorite has been used historically in metallurgy. It was used as a flux in the smelting of certain metals, particularly aluminum and steel. Its ability to lower the melting point of materials made it valuable in aiding the extraction and processing of metals.
2. Fluoridation of Water: The discovery of the importance of fluorine in dental health led to the practice of fluoridating water supplies in many parts of the world in the mid-20th century. This public health initiative aimed to reduce tooth decay and has had a significant impact on dental hygiene and the reduction of dental-related health issues.
3. Use in the Glass and Ceramic Industry: Fluorite’s low refractive index and transparency in the ultraviolet and infrared ranges have made it valuable in the glass and ceramic industry for the production of specialized glass, lenses, and optical components.
4. Fluorescent Lighting: The unique property of fluorite to fluoresce when exposed to ultraviolet light was discovered in the 19th century. This discovery played a crucial role in the development of fluorescent lighting, which is widely used in various applications, including residential, commercial, and industrial lighting.
5. Mineral Collecting and Ornamental Use: Fluorite’s vibrant colors and striking crystal formations have made it a prized mineral specimen for collectors and enthusiasts. Historically, it has been used in ornamental carvings and jewelry, adding to its cultural and aesthetic significance.
6. Scientific Research: Fluorite has been of interest to scientists for its crystallographic properties, optical characteristics, and fluorescence. It has been used in various scientific experiments, including studies related to crystallography and spectroscopy.
7. Historical Mining: Fluorite mining has played an economic role in various regions throughout history. It has been a source of income and employment for communities in areas where fluorite deposits are abundant.
8. Use in the Ceramics Industry: Certain varieties of fluorite were historically used as a flux in the ceramics industry to lower the melting point of ceramic materials, aiding in the production of ceramics and pottery.
9. Historical Healing Beliefs: In some cultures, fluorite was believed to have healing properties and was used in traditional medicine practices. While these beliefs may not have a scientific basis, they contribute to its historical cultural significance.

Overall, fluorite’s historical significance is multifaceted, encompassing contributions to industry, science, art, and culture. Its unique properties and applications have played a role in various aspects of human history and continue to be relevant in contemporary society.

Application and Uses Areas of Fluorite

Fluorite, also known as fluorspar, has a long history of applications and uses in various areas of historical significance. These applications have evolved over time, but they have left a lasting impact on different aspects of human history. Here are some of the key application areas where fluorite has played a historically significant role:

1. Metallurgy: Fluorite has been used historically as a flux in metallurgy. Its ability to lower the melting point of raw materials, such as aluminum and steel ores, was crucial in aiding the extraction and processing of metals. This played a fundamental role in early metalworking and smelting processes.
2. Glassmaking: The low refractive index and transparency of fluorite in the ultraviolet and infrared ranges have made it valuable in the glass industry. Historically, it was used to improve the optical properties of glass, especially for lenses, prisms, and optical components in telescopes and microscopes.
3. Fluorescent Lighting: The discovery of fluorite’s fluorescence in the 19th century was a critical development in the history of lighting. It paved the way for the development of fluorescent lighting, which has had a significant impact on residential, commercial, and industrial lighting, leading to energy-efficient and long-lasting lighting solutions.
4. Mineral Collecting and Ornamental Use: Fluorite’s vibrant colors and striking crystal formations have made it a popular mineral specimen among collectors and enthusiasts throughout history. Its use in ornamental carvings, sculptures, and jewelry has added to its cultural and aesthetic significance.
5. Ceramics and Pottery: Certain varieties of fluorite have been historically used as a flux in the ceramics and pottery industry. This flux helps lower the melting point of ceramic materials, facilitating the production of ceramics, glazes, and pottery.
6. Medicine and Folklore: In some cultures, fluorite was believed to have healing properties and was used in traditional medicine practices, including as an aid for treating various ailments. While these beliefs may not have a scientific basis, they contributed to its historical cultural significance.
7. Historical Mining: Fluorite mining has been an important economic activity in various regions, providing income and employment to local communities. The extraction of fluorite contributed to the development and growth of mining industries in these areas.
8. Scientific Research: Fluorite’s unique crystallographic properties, optical characteristics, and fluorescence have made it a subject of scientific interest for centuries. It has been used in various scientific experiments and studies, particularly in the fields of crystallography and spectroscopy.
9. Water Fluoridation: In the mid-20th century, the discovery of the importance of fluorine in dental health led to the practice of fluoridating public water supplies. This public health initiative has had a significant historical impact on dental hygiene and the reduction of dental-related health issues.
10. Historical Artifacts: Fluorite artifacts and objects, including sculptures and jewelry, have been discovered in archaeological excavations, providing insights into the historical use of this mineral in various cultures.

In summary, fluorite has played a historically significant role in metallurgy, glassmaking, lighting, art, ceramics, medicine, mining, and scientific research. Its unique properties and applications have contributed to advancements in technology, industry, and culture over the centuries.

Locations and Deposits

Fluorite, or fluorspar, is found in various locations around the world, and its deposits can be classified into two main types: primary (hydrothermal) and secondary (sedimentary). Here are some of the notable locations and deposits of fluorite:

Primary (Hydrothermal) Deposits:

1. China: China is the world’s largest producer of fluorite, and it has significant deposits in several provinces, including Hunan, Jiangxi, Inner Mongolia, and Zhejiang. Hunan, in particular, is famous for its rich and colorful fluorite specimens.
2. Mexico: Mexico is another major producer of fluorite, with significant deposits in states like Durango, San Luis Potosí, and Zacatecas. The mines in the state of Durango are known for producing high-quality fluorite specimens.
3. United States: Fluorite deposits in the United States are found in several states, including Illinois, Kentucky, Colorado, and New Mexico. The Cave-in-Rock mining district in Illinois is renowned for its fluorite specimens, and the Blue John Caverns in New Mexico contain fluorescent fluorite.
4. South Africa: South Africa has fluorite deposits in several locations, including the Western Cape, Northern Cape, and Gauteng provinces. These deposits are often associated with other minerals like quartz and calcite.
5. Russia: Fluorite deposits can be found in Russia, particularly in the Ural Mountains region. The Kara-Oba mine in the Altai Mountains is known for its fluorite production.
6. Canada: Canada has fluorite deposits in various provinces, including Ontario and Newfoundland. The Roger’s Mine in Ontario is known for its fluorite specimens.
7. Spain: Spain has fluorite deposits in various regions, including Asturias, Castile and León, and Andalusia. These deposits are often associated with other metallic minerals.

Secondary (Sedimentary) Deposits:

1. England: The United Kingdom has historical fluorite deposits, particularly in Derbyshire, where fluorite was mined for its use in the ceramics industry. The Blue John Caverns in Derbyshire are known for their unique and colorful fluorite specimens.
2. Germany: Germany has fluorite deposits in regions like the Black Forest, where it is often associated with other minerals like quartz and calcite.
3. Namibia: Fluorite deposits can be found in Namibia, particularly in the Okorusu mine, which has produced large and high-quality fluorite crystals.
4. Morocco: Morocco has fluorite deposits, and specimens from this region are known for their vibrant colors and unique crystal habits.
5. Peru: Fluorite is found in some mining areas in Peru, including the Huallapampa and Huayllay districts.
6. Argentina: Argentina has fluorite deposits in provinces like San Luis and La Rioja.

It’s important to note that fluorite deposits can vary in terms of the quality and quantity of fluorite they produce. Some deposits are known for producing exceptional mineral specimens that are highly prized by collectors, while others are primarily mined for industrial purposes, such as the production of hydrofluoric acid and aluminum fluoride. Additionally, the color and crystal habits of fluorite can differ significantly depending on the specific deposit and its associated minerals.

References

• Bonewitz, R. (2012). Rocks and minerals. 2nd ed. London: DK Publishing.
• Dana, J. D. (1864). Manual of Mineralogy… Wiley.
• Handbook of Mineralogy. [online] Available at: http://www.handbookofmineralogy.org [Accessed 4 Mar. 2019].
• Mineral information, data and localities.. [online] Available at: https://www.mindat.org/ [Accessed. 2019].