VENICE, Italy( Reuters)-Glassblowers in the tiny island of Murano, in the Venice lagoon, have long been famed for the colours and sophistication of their art, but a global surge in gas prices is making it hard to keep furnaces open, threatening their survival. Since glass manufacturing began on the island in the late 13th century, the industry has survived economic crises and wars, delivering prized tableware, chandeliers and jewellery to the world. Murano's glass manufacturing involves some 60