|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
Geode Sphere from