This is a natural Agate Nodule or Geode which has been cut in half with a diamond saw & Dyed or Colored Blue.
These Dyed Agate Geodes are generally made from lower grade Agate, which the Brazilian miners have always found difficult to sell, till they discovered that dying it shows off all the amazing banding and "growth" marks which you don't really see in the low grade, pale grey Agate before they're dyed.
On the outside, agate geodes appear to be nothing but rock, but looking deeper into the interior of a geode will reveal amazing crystal growth and formations. Agate geode crystals are usually composed of quartz or chalcedonic deposits, but various other minerals such as calcite, celestite and dolomite are also commonly found within other varieties of geodes.Most geodes develop in small hollow burrows within the earth, the formation begins from a small piece of limestone or anhydrite and over time, mineral-rich waters seep into the burrow allowing the minerals to harden around the small rock. It is through the repetitive series of hardening deposits from mineral-rich waters that eventually form the crystalline structure and outer crust of the geode.The crystal production that develops within a geode depends on several variables including the amount of moisture trapped within the geode, the various chemicals and rich minerals deposited, and the amount of pressure applied to the geode. If the balance of these variables is just right, crystal formations will begin to grow within the walls of the shell. The crystals build and grow inward towards the center, slowly filling the geode out. The entire process takes millions of years. Many geode specimens have been estimated to be over 250 million years old.
Average size: 50 x 30 x 20mmAverage Weight: 30g