Cobalt carbonate and cobalt oxide are earth minerals used to create blue colors in glass and ceramic. Cobalt is a very stable mineral, a strong colorant, and consistently remains blue in differing environments of temperature and atmosphere during melting processes. Any cobalt blue glass object that is ground up into powder will be blue when the powder is packed and fused. There are many sources of blue glass. It is far more likely your little beads were formerly jars and bottles.