Geodes (Greek geoides, "earthlike") are geological rock formations which occur in sedimentary and certain volcanic rocks. Geodes are essentially rock cavities or vugs with internal crystal formations or concentric banding. The exterior of the most common geodes is generally limestone or a related rock, while the interior contains quartz crystals and/or chalcedony deposits. Other geodes are completely filled with crystal, being solid all the way through. These types of geodes are called nodules.
Geodes can form in any cavity, but the term is usually reserved for more or less rounded formations in igneous and sedimentary rocks, while the more general term "vug" is applied to cavities in fissures and veins. They can form in gas bubbles in igneous rocks, such as vesicles in basaltic lavas, or as in the American Midwest, rounded cavities in sedimentary formations. After rock surrounding the cavity hardens, dissolved silicates and/or carbonates are deposited on the inside surface. Over time, this slow feed of mineral constituents from groundwater or hydrothermal solutions allows crystals to form inside the hollow chamber. Bedrock containing geodes eventually weathers and decomposes, leaving them present at the surface if they are composed of resistant material such as quartz.
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Agate Geode OCCOs 1 Kilo (2.2 lbs) Assorted 5 to 9 Pieces - Grade B |
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This is a great selection of 5 to 9 pieces that weigh approx 1 kilo (2.2 lbs). Wonderful decorative item to place around the house. Since these are natural stones no two are alike and each order there will be differences... |
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Amethyst Large Natural Crystal Geode with Calcite- Brazil |
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Amethyst Geode Crystal Sphere-Brazil |
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This amazing polished Amethyst sphere features a sparkling cavern of large and well-formed deep purple crystals, within a lighter crystal exterior. Origin is Brazil. |
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Schonbek Geometrix Geode GD0404 Silver Pendant with Strass Crystals |
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Geode Shaped something like a geodesic dome and encrusted with crystal, Geode lends itself to comparisons with celestial objects. You might see it as a satellite, a meteor or a distant moon. Geode is not a task light, but rather a whimsical illuminator of space... |
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Schonbek Geometrix Geode GD0606 Silver Pendant with Strass Crystals |
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Geode Shaped something like a geodesic dome and encrusted with crystal, Geode lends itself to comparisons with celestial objects. You might see it as a satellite, a meteor or a distant moon. Geode is not a task light, but rather a whimsical illuminator of space... |
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Schonbek Geometrix Geode GD0505 Silver Pendant with Strass Crystals |
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Geode Shaped something like a geodesic dome and encrusted with crystal, Geode lends itself to comparisons with celestial objects. You might see it as a satellite, a meteor or a distant moon. Geode is not a task light, but rather a whimsical illuminator of space... |
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Crystal Lined Oco Geode with Amethyst Crystal Pendant With Black Choker Cord |
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This is an genuine polished Oco Geode with an Amethyst Crystal mounted in the middle to be worn as a necklace or pendant. A black choker is included. Each Oco Geode is approx. 1 1/2" long and 1 1/2" wide... |
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Semi Precious Stone Geode Crystals Toggle Bracelet By Jack E Ohs NYC - Antique Gold Finish |
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Dark golden brown translucent geode with lighter gold swirls - polished front and back. Limited edition piece made in the USA by Jack E Ohs of NYC - an up and coming couture designer. We find our Jack E Ohs at gift and jewelry shows and pieces are different each time... |
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Break Your Own Geodes - Set of 12ReviewsI love these--my son loved this gift. A little harder to break that thought--a bit small. Average Rating: |
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Space Age Crystals: 6 Crystals "Amethyst & Diamond" |
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This all in one kit grows six crystals, two crystal geodes, two clusters and two single crystals. Grow three amethyst and three diamond crystals. |
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Space Age Crystals: 13 Crystals |
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Discover the forces of nature that create crystals deep inside the earth. Grow a spectacular collection of 13 mineral specimens with diameters of 2" to 8"! Dazzling crystal sculptures and geodes look like rubies, emeralds, quartz and amber... |
The size of the crystals, including their form and shade of color, vary—making each geode unique. Some contain clear, pure quartz crystals, and others have rich purple amethyst crystals. Still others can have agate, chalcedony, or jasper or minerals such as calcite, dolomite, celestite, etc. There is no easy way of telling what the inside of a geode holds until it is cut open or broken apart, however, geodes from any one locality usually have a more restricted variety of interior mineralization.
Geodes are common in some formations in the United States (mainly in Indiana, Iowa, Missouri, Kentucky and Utah). They also are common in Brazil, Namibia and Mexico. A large geode roughly the size of a minivan was discovered in Put-in-Bay, Ohio in the early 20th century. It is known as Crystal Cave, and tours are possible during the summer. In 1967, Iowa designated the geode as the official state rock, and it has a Geode State Park.
Geodes and geode slices are sometimes dyed with artificial colors. Samples of geodes with unusual colors or highly unlikely formations have usually been synthetically altered.
