Kornerupine is a mineral that belongs to the cyclosilicate group. It is composed of aluminum, boron, and magnesium, with the chemical formula (Mg,Fe)3Al6(Si,Al,B)5O21(OH). The mineral typically occurs in shades of green, but it can also be found in brown, yellow, and blue varieties. Kornerupine is known for its pleochroism, meaning it can display different colors when viewed from different angles.


History and Discovery: Kornerupine was first discovered in 1884 in Greenland by the Danish geologist Andreas Nikolaus Kornerup, after whom the mineral is named. Initially, it was misidentified as a variety of another mineral called diaspore. It wasn’t until later that kornerupine was recognized as a distinct mineral species. Over time, kornerupine has been found in various locations worldwide, including Madagascar, Sri Lanka, Brazil, Myanmar, and Tanzania.

Significance in the Gemstone World:

  1. Gemstone Use: Kornerupine is appreciated for its attractive colors and is sometimes used as a gemstone in jewelry. Green kornerupine, in particular, is popular for its vivid hues. However, its use in jewelry is relatively limited compared to more well-known gemstones.
  2. Durability: Kornerupine has good hardness and durability, making it suitable for various jewelry applications. It ranks around 6.5 to 7 on the Mohs scale of hardness, making it comparable to many other popular gemstones like peridot and tanzanite.
  3. Collectibility: While not as well-known or widely used as some other gemstones, kornerupine has gained a niche following among gemstone enthusiasts and collectors due to its unique properties and relative rarity.
  4. Pleochroism: One of the distinctive features of kornerupine is its pleochroism, where it can exhibit different colors when viewed from different angles. This optical property adds to its appeal, especially for those who appreciate gems with dynamic and changing colors.

It’s worth noting that kornerupine may not be as widely recognized as other gemstones, but its unique characteristics make it a fascinating mineral for those with an interest in gemology and mineralogy.

Geological Formation


Kornerupine typically forms in metamorphic rocks under high-pressure and high-temperature conditions. The geological processes leading to the formation of kornerupine involve the metamorphism of rocks rich in aluminum, boron, and magnesium. Here is an overview of the geological formation of kornerupine:

  1. Parent Rocks: The precursor rocks that give rise to kornerupine are often aluminum-rich rocks, such as aluminous gneisses, schists, and sometimes carbonate-rich rocks. These rocks undergo metamorphism due to tectonic forces or other geological processes.
  2. Metamorphic Conditions: Kornerupine is typically associated with high-pressure, high-temperature metamorphic environments. These conditions are often found in regions where tectonic plates collide or where rocks are subjected to intense heat and pressure deep within the Earth’s crust.
  3. Aluminum and Boron Enrichment: During metamorphism, minerals within the parent rocks undergo chemical changes. Aluminum and boron become enriched, and these elements play a crucial role in the formation of kornerupine. The presence of magnesium is also important for the formation of this mineral.
  4. Crystallization: As the metamorphic conditions reach the appropriate range, minerals start to crystallize, and kornerupine forms as elongated prismatic crystals. The crystal structure of kornerupine is classified as a cyclosilicate, where the basic building blocks are rings of silicate tetrahedra.
  5. Pegmatite Occurrence: In some cases, kornerupine may also be found in pegmatites, which are coarse-grained igneous rocks with larger crystals. Pegmatites can act as host rocks for various minerals, including kornerupine.
  6. Secondary Alterations: Kornerupine may undergo secondary alterations over time due to geological processes, leading to the formation of other minerals. These alterations can influence the color and overall appearance of kornerupine.

The geological formation of kornerupine is closely tied to the complex processes of metamorphism, which can occur over millions of years. The mineral’s occurrence in specific geological settings contributes to its relative rarity and makes it an intriguing subject of study for geologists and mineralogists.

Physical Properties of Kornerupine

  1. Color: Kornerupine occurs in a range of colors, including green (most common), brown, yellow, and blue. The green variety is often the most sought after for gemstone use.
  2. Luster: The luster of kornerupine is vitreous, giving it a glassy and reflective appearance when polished.
  3. Transparency: Kornerupine is typically transparent to translucent, allowing light to pass through, which is desirable for gemstone use.
  4. Crystal System: It crystallizes in the orthorhombic crystal system, forming prismatic crystals.
  5. Hardness: Kornerupine has a hardness ranging from 6 to 7 on the Mohs scale. This level of hardness makes it suitable for various jewelry applications.
  6. Cleavage: Kornerupine exhibits imperfect cleavage in two directions that are nearly at right angles. Cleavage refers to the way a mineral may break along certain planes.
  7. Fracture: The mineral displays a subconchoidal to uneven fracture, meaning it breaks with curved surfaces or irregular fragments.
  8. Density: The density of kornerupine typically ranges from 3.27 to 3.34 g/cm³, and it can vary depending on the composition and impurities present.
  9. Pleochroism: One of the distinctive optical properties of kornerupine is pleochroism. It shows different colors when viewed from different angles, a phenomenon that adds to its visual appeal.
  10. Optical Properties: Kornerupine has biaxial negative optical character and moderate relief. It also exhibits strong dispersion, meaning it can separate light into its component colors.
  11. Fluorescence: Some kornerupine specimens may exhibit fluorescence under ultraviolet light, appearing in various colors.

Understanding these physical properties is crucial for gemologists and those working with gemstones to identify and appreciate kornerupine. These properties also contribute to its use in jewelry and its value in the gemstone market.

Chemical Composition


The chemical composition of kornerupine is a complex arrangement of elements, and it falls within the cyclosilicate group of minerals. The general chemical formula for kornerupine is:

(Mg,Fe)3 ​ Al6 ​ (Si,Al,B)5 ​ O21 (OH)

Breaking down the components:

  • (Mg,Fe): Indicates a variable composition of magnesium (Mg) and iron (Fe).
  • Al: Aluminum is a significant component.
  • (Si,Al,B): Represents a combination of silicon (Si), aluminum (Al), and boron (B).
  • O: Oxygen is a fundamental part of the mineral’s composition.
  • OH: Hydroxide (OH) is also present in the formula.

This formula reflects the combination of different elements in various proportions, showcasing the variability in the mineral’s composition. The presence of boron is noteworthy, as it is one of the defining characteristics of kornerupine. The variable composition of magnesium and iron contributes to the range of colors observed in kornerupine specimens.

It’s important to note that the actual composition of kornerupine samples can vary, and the mineral may contain trace elements and impurities, influencing its color and overall characteristics. The chemical composition is a key factor in understanding the mineral’s formation and its properties as a gemstone.

Uses and Applications of Kornerupine

  1. Gemstone Jewelry:
    • Ornamental Use: Kornerupine, particularly in its green variety, is used as a gemstone in jewelry. It is often faceted to enhance its brilliance and can be set into various types of jewelry, including rings, earrings, and pendants.
    • Collector’s Items: Gemstone enthusiasts and collectors appreciate kornerupine for its unique properties, including pleochroism, making it a sought-after item for those interested in rare and distinctive gemstones.
  2. Metaphysical and Healing Properties:
    • Metaphysical Beliefs: Some individuals believe that certain gemstones, including kornerupine, possess metaphysical properties that can influence energy and well-being. Such beliefs vary among different cultures and are not scientifically supported.
  3. Lapidary Arts:
    • Cabochons and Carvings: Besides faceting, kornerupine may be shaped into cabochons or used for carvings and artistic creations in the field of lapidary arts.
  4. Mineral Specimen Collections:
    • Educational and Scientific Collections: Kornerupine, being a relatively rare mineral, is also valued for educational and scientific purposes. Mineral collectors and geologists may include kornerupine specimens in their collections for study and display.
  5. Decorative Stone:
    • Inlays and Decorative Items: The unique colors and optical properties of kornerupine make it suitable for decorative inlays in various items. It may be used in artistic or ornamental pieces.
  6. Research and Geological Studies:
    • Mineralogical Research: Kornerupine’s presence and properties in specific geological settings provide valuable information to geologists and mineralogists studying metamorphic processes and rock formations.
  7. Limited Industrial Applications:
    • Limited Use in Industry: While not a common industrial material, kornerupine has been explored for potential uses in certain specialized applications due to its hardness and resistance to wear.

It’s important to note that kornerupine, although appreciated for its unique qualities, is not as widely used in the jewelry market as more mainstream gemstones. Its application is often niche, catering to those who seek distinctive and less common gemstone options.

Occurrence and Mining Locations


Kornerupine is a relatively rare mineral, and its occurrences are scattered across various locations globally. The mineral is often associated with certain geological settings, particularly those involving high-pressure and high-temperature metamorphic processes. Here are some notable occurrences and mining locations for kornerupine:

  1. Greenland:
    • Discovery Location: Kornerupine was first discovered in 1884 in Greenland by the Danish geologist Andreas Nikolaus Kornerup, after whom the mineral is named.
    • Occurrences: Greenland remains one of the historical and notable sources of kornerupine.
  2. Madagascar:
    • Occurrences: Madagascar is a significant source of kornerupine, and the mineral is found in various regions on the island. The green variety from Madagascar is particularly valued in the gemstone market.
  3. Sri Lanka:
    • Occurrences: Sri Lanka has been known to produce kornerupine, and the gem-quality material from this location may exhibit various colors.
  4. Myanmar (Burma):
    • Occurrences: Myanmar is another country where kornerupine can be found. The mineral occurs in certain gem-bearing regions of the country.
  5. Brazil:
    • Occurrences: Brazil has been recognized as a source of kornerupine, contributing to the global availability of the mineral.
  6. Tanzania:
    • Occurrences: Tanzania is known to produce kornerupine, and the mineral has been found in specific regions within the country.
  7. Kenya:
    • Occurrences: Kornerupine has also been reported in Kenya, contributing to the mineral’s global distribution.

It’s important to note that while kornerupine occurs in these locations, the quantity and quality of the material may vary. Gem-quality kornerupine suitable for use in jewelry is often obtained through mining operations that focus on extracting and processing gemstones. Additionally, the mineral may also be found in pegmatites, contributing to its presence in certain geological formations.