Falcondoite , Willemseite Locality: Loma Peguera, Bonao , Monseñor Nouel Province , Dominican Republic ( Locality at mindat.org ) Size: 4.3 x 3.0 x 0.3 cm. Falcondoite and willemseite are rare nickel, magnesium silicates found in a serpentinized harzbergite massif or an obducted ophiolite at a plate collision of oceanic crust with continental crust. The locality is in the Dominican Republic, which is the Type Locality for falcondoite. This very showy, bright green thin crust is mostly green falcondoite, with just a bit of lighter, olive willemseite. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Willemseite
Willemseite is an IMA-recognized mineral species in the silicate class, with the chemical formula Ni₃Si₄O₁₀(OH)₂.
It crystallizes in the monoclinic crystal system. It is a member of the Clay, Talc structural group.
Key properties: Mohs hardness 2; specific gravity 3.31; optically biaxial.
IMA symbol Wls, IMA status: approved, named in 1969.
Found as a secondary mineral in a nickel-bearing layered igneous sill.
It is found associated with Ferroan trevorite, nimite, violarite, millerite, reevesite, goethite, \opal.".
The name refers to Johannes Willemse, Professor of Geology, University of Pretoria, Pretoria, South Africa.