Macrophotograph of the mineral amethyst (Silicon dioxide); a form of quartz that came to be a symbol of celibacy in the Middle Ages; found in Uruguay. Image #2286
Macrophotograph of a piece of calcite and aragonite from the Sonoran Desert of Mexico Image #2272
Macrophotograph of the colors and patterns in a cut and polished slab of brecciated pink opal. An opalised radiolarite from Western Australia. Radiolarite is a sedimentary rock composed primarily of the microscopic skeletal remains of radiolara protozoa. Image #3842
