Slice of amethyst geode bordered with agate

Initially there is an air bubble in Brazil: basaltic lava loaded with gas rising to the surface of the earth releases gas bubbles that have sometimes remained blocked by the viscosity of the cooling lava. These cavities will receive silica deposits brought by hydrothermal solutions. Each new infiltration will bring different oxides, and therefore different colors: hematite, manganese, limonite, greenish chlorite... After the beautiful deposits of golden agate, the geode ended by a crystallization of pale Amethyst. Picture 6 shows the brightness of the colours when a light passes through it. 5 slices were cut from this geode.