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.

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.

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.

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.