Amethyst Geode Spheres
What Is A Geode?
The mysterious earth-shaped geodes have long challenged geologist to explain how they are formed. Geodes are a variable phenomenon and, therefore, many theories exists to explain how they are created. The term geode is derived from the Greek word Geoides which means "earth like." A geode is a sphere shaped rock which contains a hollow cavity lined with crystals. A geode which is completely filled with small compact crystal formations such as agate, jasper or chalcedony is called a nodule. The only difference between a geode and a nodule is that a geode has a hollow cavity, and a nodule is solid.
How Geodes Are Created
Geodes begin as bubbles in volcanic rock or as animal burrows, tree roots or mud balls in sedimentary rock. Over time, the outer shell of the spherical shape hardens, and water containing silica precipitation forms on the inside walls of the hollow cavity within the geode. The silica precipitation can contain any variety of dissolved minerals, the most common being quartz, but amethyst and calcite are also found.
Over a period of thousands of years, layers of silica cool, forming crystals of different minerals within the cavity. Different types of silica cool at varying temperatures, thus creating layers of different types of mineral crystals. Each geode is unique in composition and can only be truly discovered when cracked open or cut with a rock saw. The size and formation of crystals and different shades of color within the crystals make each geode special. The rough exterior of the geode gives no indication of the secrets held within its core. The anticipation never fades for those who curiously collect buckets full of round geodes and eagerly expose the secrets of each individual sphere-shaped rock. The most prized contain rare amethyst crystals or black calcites.
The amethyst geode is one of the most captivating and beautiful geodes ever found. Each one is uniquely shaped by nature, their shells lined with thousands of purple amethyst crystals. In only one place on earth are these high quality amethyst geodes found, the Brazilian -Uruguayan border of South America. These wonders that have taken nature millions of years to create started out as a gas bubble from a magmatic flow. In the following epoch, ground water would slowly permeate the cavity, depositing its dissolved mineral deposits, slow enough for the dissolved minerals to assemble into their unique crystal form
in the case of the Rio Grande do Sol region of Brazil, the circumstances of that environment were very special because of the silicon and iron /manganese minerals present. The geode cavities were to be filled with the amethyst crystal, possessing a deep, beautiful purple tone. Perhaps nowhere on earth is a more beautiful geode created.
68mm Amethyst Geode Sphere from Brazil
2.68" (68mm) Polished Amethyst Crystal Geode Sphere from Brazil
This is an amazing amethyst geode sphere from Brazil. This type of sphere is rare due to the extreme difficulty to cut. It has a medium grape color amethyst and has beautiful crystals in it. There is one Amethyst crystal missing from the otherwise museum quality 2" x 1" x 1 1/2" Amethyst Crystal Vug.
This sphere was cut and polished in Brazil.