This bowl is handblown using Calcedonia color bar. Calcedonia glass was developed in 1460 in Murano, Italy. Its striations mimic those of an agate. The colors, shades, and markings result from a chemical process intrinsic to each batch of glass; a reaction based on the effect of the metal silver on the other minerals and substances used to make glass. Pieces from the same bar can be either opaque or clear. This clear piece has streaks of milky blue and brown.