Chalcedony     El Cobre, Aguascalientes, Mexico.  Ex. Dr. Steve Chamberlain collection.   This unusual specimen is from the early 1960s (1962) and is a .6 cm thick plate measuring 4.2 x 3 cm overall.  It is lustrous and a light copper color.  It is composed of layers of quartz which exhibit nice banding when viewed on edge.  No damage and nice aesthetics.  $35