Kutnohorite: Properties, Uses, Occurrence
Kutnohorite is a rare calcium manganese carbonate mineral with magnesium and iron that is a member of the dolomite group. The crystals often occur in rounded granular masses, sometimes in fan, but rarely in single crystals.
Kutnohorite was first described in 1901 by A. Bukowsky. The name kutnohorite is derived from the type locality of Kutná Hora, Czech Republic.
Kutnohorite occurs as aggregates of bundled blades of white through rose pink to light brown crystals. Also as simple rhombs with curved faces, polycrystalline spherules and in massive and granular habits. It has perfect rhombohedral cleavage, typical of carbonates. It is brittle with a subconchoidal fracture and it is quite soft, with hardness 3.5 to 4, between calcite and fluorite. Specific gravity is 3.12, denser than both dolomite and calcite. It is soluble in acids, as are all carbonates.
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| Kutnahorite Specimen From the Kalahari Manganese Field, Northern Cape, South Africa Photo: Rocks of Africa./E-rocks |
Kutnohorite is found in a variety of geologic settings, including sedimentary rocks, hydrothermal veins, and metamorphic rocks. It is often associated with other carbonate minerals, such as calcite, dolomite, and ankerite.
Kutnohorite occurs typically in manganiferous sediments, associated with rhodochrosite, aragonite and calcite.
Uses of Kutnohorite
Kutnohorite, while valued for its aesthetic qualities among mineral enthusiasts, is not widely utilized for industrial or commercial purposes due to its scarcity. Its primary significance lies in geological studies, mineralogy research, and as a collector's item. Here are some aspects of kutnohorite's uses:
Mineral Collecting:
Kutnohorite's vibrant pink color, unique crystal formations, and relative rarity make it a sought-after specimen among mineral collectors. Its aesthetic appeal and distinctiveness contribute to its desirability within the collector community.
Scientific Research:
Kutnohorite holds scientific importance as a subject of study in mineralogy and geology. Researchers examine its crystal structure, chemical composition, and occurrence patterns to gain insights into geological processes, mineral formation, and the coexistence of minerals within specific geological environments.
Educational Purposes:
Kutnohorite serves educational purposes in geology and mineralogy courses. Its unique characteristics make it a valuable example for students studying mineral identification, crystallography, and the geological conditions that give rise to specific minerals.
Specimen Display:
Museums and mineral exhibits often showcase kutnohorite specimens to highlight the diversity and beauty of minerals found in the Earth's crust. The mineral's distinctive pink coloration makes it visually appealing and contributes to the educational value of these displays.
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| Pink kutnohorite crystals from N'Chwaning II Mine, Kalahari Mn Field, South Africa Photo: © Weinrich Minerals. |
Properties of Kutnohorite
Class: Carbonates, Group: Dolomite
Composition: CaMn²⁺(CO₃)₂ - This formula reveals Kutnohorite is a calcium manganese carbonate, often containing trace amounts of iron and magnesium. Think of it as a blend of calcite and rhodochrosite, with manganese adding its distinctive pink touch.
Color: Predominant: Pink, ranging from pale to vibrant shades. The pink intensity depends on the manganese content, making it a natural color indicator. Variations: Light brown, white (translucent crystals). These colors arise from the presence of other elements like iron or impurities.
Transparency: Crystals: Translucent, allowing light to pass through partially, showcasing the internal structure and color depth. Massive forms: Opaque, blocking light completely due to their dense and tightly packed structure.
Luster: Pearly, vitreous, to dull; Dependent on crystal habit and surface condition.
Streak: White to pale pink; Reveals the intrinsic color of the mineral.
Hardness: 3.5 - 4 on the Mohs scale; Moderately soft, can be scratched by steel or harder materials.
Cleavage: Perfect rhombohedral cleavage in three directions; Breaks readily along specific planes.
Fracture: Conchoidal; When broken along non-cleavage planes, exhibits smooth, curved surfaces.
Crystal Habits and Forms: Simple rhombs with curved faces, fan-shaped aggregates, massive and granular forms.
Density: 4.6 g/cm³
Specific Gravity: 3.12; Denser than most minerals, including calcite and dolomite.
Solubility: Soluble in acids; Like other carbonates, dissolves in acidic solutions.
Magnetism: Non-magnetic; Does not interact with magnets.
Fluorescence: None to weak; Does not typically fluoresce under ultraviolet light.
Pleochroism: Weak in some cases; Exhibits slight color variations depending on viewing direction.
Refractive Index: No = 1.710 - 1.727, Ne = 1.519 - 1.535; Useful for mineral identification.
Inclusions: May contain inclusions of other minerals; Tiny mineral inclusions can be present, influencing appearance and properties.
Notable Occurrences include Tuscany, Italy and Kank, Kutna Hora, Czech Republic.
Best Field Indicators are pink color, crystal habit and density.
Name: Named in 1901 by Antonín Bukovský for the type locality - Kutna Hora, Bohemia, Czech Republic.
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| Kutnohorite Crystals. Wessels Mine, Hotazel, Kalahari manganese fields, Northern Cape Province, South Africa Copyright © Rob Lavinsky |
Kutnohorite Occurrence
Kutnohorite is a relatively rare mineral found in various geological settings. Here are some notable locations where it occurs:
Hydrothermal Veins:
- Långban, Sweden: Associated with manganese oxides and other carbonates.
- Franklin Furnace, New Jersey, USA: Found in association with willemite and zincite.
- Tsumeb Mine, Namibia: Occurs in veins with other sulfide and carbonate minerals.
Metamorphic Rocks:
- Úrkút Manganese Mine, Hungary: Found in fossiliferous concretions composed mainly of rhodochrosite.
- Wessels Mine, South Africa: Occurs in manganese-rich metamorphosed sedimentary rocks.
Sedimentary Manganese Deposits:
Tuscany, Italy: Found in association with rhodochrosite, aragonite, and calcite.
Kank, Kutná Hora, Czech Republic (type locality): Occurs in manganese-rich sedimentary rocks.
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| Kutnohorite |
In conclusion, kutnohorite, with its calcium manganese carbonate composition and distinctive pink coloration, stands as a subject of scientific inquiry. By rigorously examining its chemical properties, physical characteristics, and geological occurrences, researchers contribute to the broader understanding of mineralogy. Kutnohorite's significance extends beyond its aesthetic appeal, offering valuable insights into Earth's geological processes and the intricacies of mineral formation.
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