Obsidian — specimen 0742, photo © NMNHS
Weight: 1.20 ct; size: 6.75 | 5.79 | 3.47 mm; shape: rectangle; colour: black; clarity: opaque; cut: excellent; treatment: none.
Clean specimen; design ‘Rectangulum Cab’, excellent cut by Tan Pen.
More information from ‘Classification’
A rock; a mixture of cryptocrystalline grains of silica minerals in a glass-like suspension.