Geodes are technically sedimentary rocks, since they are the result of the action of water. Geodes are formed when cavities in a host rock (which may be sedimentary or igneous) become lined with a durable mineral, often a variety of quartz.
Inside and outside views of the geode. Geodes (Greek γεώδης - ge-ōdēs, earthlike) are geological secondary structures which occur in certain sedimentary and volcanic rocks. When a geode is broken, as in the example above, the minerals inside are revealed. Most geodes are completely filled with minerals, most often quartz. The quartz can be massive, crystalline, or layered, which is a variety called agate. But when most people think of geodes they think of spherical rocks that are hollow.  Geodes are created in the hollow areas of soil such as animal burrows or tree roots. They are also formed in the bubbles in volcanic rock. Over time, dissolved minerals seep into a hollow area and harden into an outer shell creating the geode. Geodes are rocks that are plain on the outside but can have beautiful crystals on the inside. In the Greek language, geode means shape of the earth, and geodes are round like earth or oblong like an egg. Geodes are common in the U.S. states of Indiana, Iowa, Missouri,  Kentucky and Utah, and the countries Mexico, Brazil, and Namibia. 1  All about Crystal Geodes A crystal geode is a plain-looking rock on the outside. 2  When you split it open, a hollow rock with a crystalline structure is inside. Answer   No. The term geode is used to refer to a cavity or vug in sedimentary or igneous rock that is lined or completely filled in with mineral deposits or crysta … ls. These deposits are formed from the mineral rich water that enters the cavity. Large geodes for sedimentary geodes would be any geode over the size of 6 to 8 inches. Volcanic geodes are considered large after 4 to 5 inches. The hollowness of a geode also contributes to the value. The more hollow the geode the bigger the crystals and more minerals that can be found inside.  Geologists have long been challenged to explain how geodes, those mysterious spherical rocks, are formed. Geodes are a variable phenomenon, which means that they may be created in various different ways. The term geode is derived from the Greek word Geoides which means earthlike.. A geode is a round rock which contains a hollow cavity lined with crystals. Rocks which are completely filled with small compact crystal formations such as agate, jasper or chalcedony are called nodules. The only difference between a geode and a nodule is that a geode has a hollow cavity, and a nodule is solid Geodes (Greek γεώδης - ge-ōdēs, earthlike) are commonly independent spherical masses of resistant mineral matter that are usually hollow. The extreme filling of a geode so that it is solid is also common. Some people refer to completely in-filled geodes as nodules, but the two names are not always consistently used.  Geodes can also form in sedimentary rocks such as limestone or sandstone. The cavity in these rocks is usually formed from a solid core. A mass of minerals, or nodule, in the sediment may begin to dissolve and leave space behind. The next step, for both igneous and sedimentary geodes, is for mineral-rich groundwater or rainwater to seep through the porous rock and fill the cavity. The water lines a thin crust of minerals inside of the cavity. As water flows through the geode, additional mineral layers are deposited in its hollow interior. Bitaba birds are not real, but geodes are real rocks. Geodes are rocks that are plain on the outside but can have beautiful crystals on the inside. In the Greek language, geode means shape of the earth, and geodes are round like earth or oblong like an egg. They can be a couple inches or several feet in size GEODES. Like: Share: Geodes are technically sedimentary rocks, since they are the result of the action of water. Geodes are formed when cavities in a host rock (which may be sedimentary or igneous) become lined with a durable mineral, often a variety of quartz. The term geode usually refers to rounded nodules with hollow centers
https://en.wikipedia.org/wiki/Geode http://www.uky.edu/KGS/rocksmn/geodes.htm http://www.magickeys.com/books/bitaba/geodes.html http://www.answers.com/Q/What_are_geodes http://www.ebay.com/gds/What-is-a-geode-What-minerals-are-rare-/10000000000835958/g.html http://www.desertusa.com/desert-prospecting/geode.html http://www.mindat.org/min-7628.html http://scienceline.org/2012/11/where-do-geodes-come-from/ http://www.magickeys.com/books/bitaba/geodes.html http://www.galleries.com/rocks/geodes.htm
what are geodes