Vintage Blue Givre Cocktail Brooch Porphyry Art Glass & Rhinestones Pin

A large faceted and beautifully swirled lampworked porphyry or givre glass stone, is featured in this vintage mid-century cocktail brooch, circa 1950s/60s. 

The well made unsigned pin has a silvertoned filigree base in triangular shape, and prong set with a faceted triangular art glass stone of deep cerulean blue with creamy interior striation or swirl.

It is surrounded with a border of sapphire blue rhinestones, measures approximately 2 inches across, by 1&5/8 inches high at its highest point, and weighs 34.3 grams.