Custom Designed Stained Glass with Agate Geodes
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, often created by animals or depressions left by tree roots. 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. Surprisingly, the majority of agate geode specimens are never completely filled out. Geodes with filled out crystal formations are referred to as nodules; nodules composed of agate are referred to as 'thundereggs'.
Geodes can also develop within bubbles of volcanic rock. Minerals get trapped within cavities deposited through steam and with each deposit, the various minerals harden and form around a seed rock, typically limestone. Crystal development will vary based on the rate and duration of moisture deposits. If water was deposited slowly and with very few impurities, the geode crust will be finely lined with crystal, but if moisture deposits were rapidly made, the cavity will develop with bands of quartz, usually as banded agate.
Agate is a variety of chalcedony that forms in concentric layers in a remarkable variety of colors and textures. The crystals vary in clarity from opaque to translucent to transparent. Agate quartz was highly valued as a talisman or amulet during ancient times, and to this day, are still one of the most popular jewelry gemstones, often seen in accessories from rings to pendants, to earrings and now the stained glass works of Fine Art by J.Neil. Agate geodes are often displayed as ornaments on pedestals, and many owners will place them strategically around their homes and gardens for their metaphysical and therapeutic abilities, similar to the concept of feng shui. Agate is found in many locations in the world, including Brazil, Uruguay, Australia, India, China, Madagascar, Mexico, Mongolia, Namibia and the USA.
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