Kochite: Properties and Occurrences

Kochite is a rare silicate mineral with a chemical formula of (Na, Ca)3Ca2(Mn, Ca)ZrTi [(F, O)4(Si2O7)2 or double that. It is a triclinic-pinacoidal mineral containing aluminum, calcium, cerium, fluorine, hafnium, iron, lanthanum, manganese, niobium, oxygen, silicon, sodium, strontium, titanium, vanadium, yttrium, and zirconium. Kochite is a member of the rosenbuschite group.

As the stage of the microscope is turned from X to Z the color changes from colorless to a pale brownish-yellow. It is also a birefringent mineral, showing bright colors under crossed polarization.

General Information:

  • Category; Sorosilicates
  • Rosenbuschite group
  • Formula: (Na,Ca)3Ca2(Mn,Ca)ZrTi [(F,O)4(Si2O7)2
  • Crystal system: Triclinic
  • Crystal class: Pinacoidal (1) (same H-M symbol)

Fig: Kochite

Properties

Kochite is an anisotropic mineral. The light entering the mineral is split into two rays that vibrate at 90° to each other. It is biaxial, meaning it has two optic axes (lines of symmetry). In plane-polarized light, this mineral is colorless to light brown and is pleochroic.

  • Color: Colorless to light brown
  • Crystal habit: Acicular to lath-shaped prismatic crystals
  • Cleavage: {100} perfect
  • Fracture: Uneven
  • Tenacity: Brittle
  • Mohs scale hardness: 5
  • Luster: Vitreous
  • Streak: White
  • Diaphaneity: Transparent
  • Specific gravity: 3.32
  • Optical properties: Biaxial (+)

Discovery and occurrence

Kochite is found in the alkaline igneous complex of East Greenland and is named after Danish geologist Lauge Koch (1892-1964), a geologist who overturned the previous conception of Greenland’s landscapes.

Kochite is the titanium – manganese analog of rosenbuschite. It occurs in nepheline syenite associated with nepheline, alkali feldspar, and låvenite in the Werner Bjerge alkaline complex along the eastern coast of Greenland.

 

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