Agate — specimen 0620, photo © NMNHS
USA, Montana, Yellowstone River
Weight: 3.78 ct; size: 13.85 | 10.01 | 3.27 mm; shape: oval; colour: medium dark red; very slightly brownish; clarity: translucent; cut: very good; treatment: none.
Clean specimen; very good cabochon style cut.
More information from ‘Classification’
A variety of chalcedony with layered structure.