A first natural occurrence of triclinic sincosite, ca(Vo)2(po4)2∙4h2o, from the south rasmussen ridge mine, Idaho, USA

Abstract

A single-crystal structure analysis of sincosite from the South Rasmussen Ridge mine, Idaho, USA has con-firmed it as the first natural occurrence with triclinic symmetry. Previous work on the mineral, based on limited electron diffraction and single crystal studies, together with the indexing of powder X-ray diffraction data, have described it as having tetragonal symmetry; although hydrothermally prepared synthetic sincosite is triclinic. The unit cell parameters are a = 6.3531(12), b = 6.3567(14), c = 6.6050(18) Å, α = 106.995(22), β = 94.115(19), γ = 90.006(16)°, and the space group is P1. The crystal structure was refined to wRobs = 0.11 for 783 reflections with I > 4σ(I). The structure..