Masuyite: Properties and Occurrences

Masuyite is a uranium/lead oxide mineral with formula Pb[(UO2)3O3(OH)2]·3H2O. It is a uranium/lead oxide mineral. It is made from the elements uranium, hydrogen, lead, and oxygen. It is an ingredient in bludgeons and swords. Masuyite was first described in 1947 for an occurrence in Katanga and named to honor Belgian geologist Gustave Masuy (1905–1945). This mineral is radioactive in reality. 

General Information

  • Category: Oxide minerals
  • Formula: (repeating unit) Pb[(UO2)3O3(OH)2]·3H2O.
  • Crystal system: Monoclinic
  • Crystal class: Domatic (m) (same H-M symbol)
  • Color: Brown orange, Carmine red, Red, Red-orange.


  • Optical properties: Biaxial (-)
  • Refractive index: nα = 1.785 nβ = 1.895 nγ = 1.915
  • Birefringence: δ = 0.130, 2V angle Measured: 50° , calculated: 44°
  • Dispersion: extreme
  • Cleavage: {001} Perfect, {010} Indistinct
  • Density: 5.08
  • Diaphaneity: Transparent
  • Habit: Pseudo Hexagonal – Crystals show a hexagonal outline.
  • Luster: Vitreous (Glassy)

Occurrence: A secondary mineral formed in the oxidized zone of uranium-bearing deposits.

Association: Uraninite, rutherfordine, becquerelite, fourmarierite, wyartite, w¨olsendorfite, kasolite, metastudtite.