Santite,a new mineral phase from Larderello,Tuscany

A new borate mineral has been found in a sample from Larderello, mixed with larderellite and lesser amounts of sassolite. The mineral is never well crystallized, but it constantly appears as very small, clear and colourless grains; its refractive indices are: =1.422, =1.435, =1.480. Single-crystal X-ray photographs show that the mineral is orthorombic with cell dimensions: =11.10 Å, b=11.18 Å, c=9.08 Å. X-ray powder diffraction and partial chemical analyses carried out on the whole sample (it being impossible to separate a sufficient quantity of pure material) confirm the foregoing data, according to which the mineral may be considered as the natural equivalent of the synthetic compound KB₅O₈ · 4H₂O. It is likely that it originated from the reaction between potassium-bearing hot solutions and primary deposits of larderellite. It is named for the Tuscan naturalist Giorgio Santi.This new mineral has been approved by the Commission on New Minerals and New Mineral Names of the International Mineralogical Association.This research was supported by Consiglio Nazionale delle Ricerche, Roma.