Agate Geode Gemstone Information


By Gavin ClarkeReviewed By Andreas Zabczyk

Agate Geode Gemstone Information

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About Agate Geodes – History and Introduction

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.

  • Identifying Agate Geode
  • Agate Geode Origin
  • Buying Agate Geode
  • Agate Geode Gemological Properties
  • Agate Geode Varieties
  • Agate Geode Mythology
  • Agate Geode Jewelry
  • Agate Geode Gemstone Care
Agate Geode Gemstone
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Identifying Agate Geode Back to Top

Identifying geodes requires a great amount of skill. Untrained eyes will struggle to identify geodes because of their plain appearance. Skilled miners focus on the outcrops of rock and look specifically in environments where geodes are most likely to develop. Miners will look for any egg-shaped stones or unusual stones with cauliflower-like formations.

Agate Geode Origin and Gemstone Sources

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The term ‘geode’ originated from a Greek term meaning ‘shape of the earth’. The name was likely given because of their natural, round earth-like formations, although most occur in oblong or egg-like shapes. Geodes can be found all around the world, but they are mostly located in deserts and volcanic regions. Geodes are especially abundant throughout America including California, Illinois, Nevada, Arizona, Missouri, Kentucky, Utah and Iowa.

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.

Buying Agate Geode and Determining its Gemstone Value

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Geode prices vary greatly in the gem market. Some smaller geodes may fetch as little as one to two dollars, while larger specimens have been known to command several thousand dollars or more. Geode prices depend entirely on the crystal growth, size and weight.

Agate Geode Color

Geodes occur in a wide range of vivid colors, depending on the type of crystals within. Typically, geodes contain near-colorless quartz, but amethyst crystals and other colors can also be found. Geode crystals form their own unique pattern of natural facets, which naturally heightens the brilliance, fire and intensity of color.

Agate Geode Clarity and Luster

Geode clarity depends on the type of crystal within. Cryptocrystalline growths are translucent to opaque with waxy to dull luster. Macrocrystalline quartz growths are typically transparent to translucent with vitreous luster.

Agate Geode Cut and Shape

Agate geodes typically develop with ovular shape. During the production process, they are sliced open to expose the crystal formation. The crystal-side is cut flat and lightly polished. The rough exterior acts as the base and is left in its natural untreated state.

Agate Geode Treatment

Agate geodes are typically untreated, but some specimens may be enhanced. Even though geodes can occur naturally with bright and vivid colors, if the colors appear too vivid or artificial, there’s a good chance they may have been synthetically altered or dyed.

Agate Geodes Gemological Properties:

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**Dependent on actual crystal composition**
Chemical Formula: SiO2 – Silicon dioxide
Crystal Structure: Cryptocrystalline – Microcrystalline aggregate (trigonal)
Color: All colors, multicolored and banded
Hardness: 6.5 – 7 on the Mohs scale
Refractive Index: 1.530 – 1.540
Density: 2.60 – 2.64
Cleavage: None
Transparency: Translucent to opaque (depends on actual crystal composition.)
Double Refraction / Birefringence: Up to 0.004
Luster: Waxy – dull
Fluorescence: Varied based on bands: yellow, green, blue-white; slightly strong

Agate Geode Gemstone Varieties or other Similar Gemstones:

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Agate geodes can occur in a wide variety of colors and patterns. Most trade names or varieties are simply names that refer to the locality or region that the geode was formed. Other varieties of geodes are sometimes named after the crystal growth itself. Other popular geodes, include citrine geodes and amethyst geodes. In many cases, geodes are confused with drusy gemstones.

Druzy gemstones exhibit tiny crystals, rather than larger crystal growths, that formed within or on the surface of another mineral. Both drusy gemstones and geode gemstones are often cut into flat plates rather than rounded half-egg shaped stones. These types of stones are often referred to as ‘crystal clusters’ or ‘crystal plates’.

Most Popular Similar or Related Gemstone Varieties – Trade Names:

Amethyst geode, citrine geode, azurite drusy, rainbow pyrite drusy, thunderegg, Bristol diamonds, quartz geode, chalcedony geode, jasper geode, limonite geode and calcite geode are among the most common varieties of geodes and drusys.

Lesser Known Similar or Related Gemstone Varieties – Trade Names:

Uvarovite garnet drusy, hemimorphite drusy, dolomite geode, celestite geode, pyrite geode, kaolinite geode, sphalerite geode, millerite geode, barite geode coconut geode and smithsonite geode are among the lesser known geode and drusy trade names.

Agate Geode Gemstone Mythology, Metaphysical, Alternative Healing

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Agate geodes carry the same healing powers as all other agate crystals. In addition, most geodes contain other minerals, thus carrying the powers of all minerals contained within.

Geodes in general are known to have very strong powers. Geodes are believed to be able to help see the ‘whole perspective’ and to see situations from different viewpoints. Agate geodes are also believed to be able to help shape someone’s future. They can bridge communications and they are also helpful for clearing one’s mind for meditation. Agate geodes are especially powerful in alleviating stress and strengthening spirituality.

Disclaimer: Metaphysical and Alternative Crystal Healing Powers and Properties are not to be taken as confirmed advice. Should you have any medical conditions, please see a licensed practitioner. This information is not to replace the advice of your doctor. GemSelect does not guarantee any claims or statements made. cannot be held liable for the information contained herein under any circumstances.

Agate Geode Gemstone and Jewelry Design Ideas

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Agate geodes are unusual in shape, so most are sliced when used in jewelry designs. Agate geodes are very popular for gemstone jewelry, carvings, cameos, beads and cabochons. Geodes make excellent ornamental gems and are most ideal for pendants, pins, brooches or earrings.

Note: Buy colored gemstones by size and not by carat weight. Colored stones vary in size-to-weight ratio. Some stones are larger and others are smaller than diamonds by weight in comparison.

Agate Geode Gemstone and Jewelry Care and Cleaning

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How to Clean your GemstonesAgate geodes should be cleaned using plain water and mild soap. Using a soft cloth may not be efficient when trying to clean crevices. A soft brush, such as a toothbrush,can be used to clean geodes but care should be taken to ensure not too much pressure is applied. Do not use any harsh chemicals or cleaners to clean geodes and rinse only with room temperature water. Geodes can also be soaked in water to help soften and remove hardened debris.

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