Characterization and isolation of a natural stilbite from Atacama region, Chile.

Abstract

The properties of natural stilbite from the Atacama region of Chile are described in this work. This mineral shows colorless, white and honey-brownish shades, and it presents pearly and vitreous luster with a radial crystallization form. The results from the physical and chemical characterization are the following: Mohs hardness = 3-4, specific gravity = 2.05, mass loss by heating = 17.4% and mass loss by HCl dissolution = 35.5%. The chemical composition is Na (0.59%), Ca (5.64%),Al (9.40%), Si+O (66.93%), H2O (17.44%).The X-ray diffraction patterns match also very well with stellerite, a Na-free orthorhombic zeolite (stilbite is recognized as monoclinic), suggesting the presence of two different crystal growing sectors. The IR spectrum shows the characteristic O-H stretching and bending and the symmetric and asymmetric T-O (T: Si, Al) stretching absorption bands. Gravitational combined with magnetic separation methods seems to be appropriated for separating the stilbite from the associated gangue.