Almarudite is an extremely rare alkaline manganese beryllium silicate mineral of the cyclosilicates (ring silicates) class, with the formula written as K([], Na)2 (Mn2+, Fe2+, Mg)2 (Be,Al)3[Si12O30], from the volcanic environment of the Eifel Mountains, Germany.

Almarudite is a hexagonal-dihexagonal dipyramidal mineral containing aluminum, beryllium, calcium, iron, magnesium, manganese, oxygen, potassium, silicon, sodium, and zinc.

General information:

  • Hardness: 6
  • Specific Gravity: 2.71
  • Crystal System: Hexagonal
  • Member of: Osumilite Group
  • Tenacity: Brittle
  • Density: 2.71 g/cm3 (Measured)

They are embedded in a carbonate-quartz matrix and are associated with ettringite/thaumasite, mayenite, cuspidine, larnite, “calcio-olivine”, tobermorite, portlandite, hydrocalumite, a member of the ellestadite series, magnetite and hematite.

Physical Properties of Almarudite

Almarudite has been found in a single silicate-rich xenolith. It forms euhedral, platy crystals flattened on {0001}, with a maximum diameter of about 1.5 mm and a maximum thickness of 0.2 mm. It is associated with tridymite, sanidine, “clinopyroxene”, “amphibole”, quartz, hematite, sillimanite and rare braunite. Almarudite is yellow to orange, with a light orange streak and vitreous luster.

  • Cleavage: None
  • Color: Yellow, Orange.
  • Diaphaneity: Transparent
  • Fracture: Brittle – Irregular – Very brittle fracture producing irregular fragments
  • Habit: Euhedral Crystals – Occurs as well-formed crystals showing good external form.
  • Habit: Tabular – Form dimensions are thin in one direction.
  • Luster: Vitreous (Glassy)
  • Streak: light orange


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