Antique late 18th century Portuguese ring with stones traditionally described as Minas Novas

A late 18th century Portuguese ring, its elongated silver head densely set with colourless stones traditionally described as Minas Novas, most probably rock crystal, mounted on a yellow gold hoop. The jewel belongs to a distinctive tradition of Portuguese jewellery in which foil-backed colourless stones were used to create a rich, luminous effect reminiscent of diamond-set jewellery.