Blue Glass Czech Clip-On Earrings Intricately cut Blue Czech Glass clip-on earrings in a brass surround with inlays. The earrings measure 3/4" in diameter Czech glass is made in the Czech Republic, centralized around an area called Jablonec nad Nisou. Production of glass in the area dates back to the 14th century, though production was depressed under communist rule. Because of this long tradition, their workmanship and quality has an excellent reputation.