Overall Dimension (including bail): 2.2 x 0.7 x 0.25 inches
Inner Bail Diameter: 5 mm
Weight: 9.2 grams
Stamp/Mark: Starborn, 925
Serial Number: p27081
Obsidian is volcanic glass, considered a rock rather than a mineral. It is formed in the last stage of basaltic eruptions, when the silicas, left over after most other elements have been used up, are ejected and chilled at surface temperatures. Rainbow obsidian has a multicolored iridescence.