Geodes are mostly found in deserts, volcanic ash beds and areas with limestone throughout the world. In the United States, common geode sites include Arizona, California, Iowa, Nevada and Utah. The most abundant geode sites in California are Riverside and Imperial counties.Know More
According to DesertUSA, one of the most popular geode areas is known as the Hauser Geode Beds, which are found at Wiley Well in Imperial Valley, California. Other well-known places with the finest concentration of geodes are the Cinnamon Geode Beds and the North Black Hills Geode Beds.
Geodes are found in volcanic rocks and sedimentary rocks such as limestone and dolomite. They form in sedimentary rocks when cavities are dissolved by ground water and minerals are deposited again as crystals. Additionally, they form in pre-existing concretions and spaces caused by expansion of rocks due to internal fluid pressure.
Geodes typically have minerals like carbonates, a crystal lining of quartz and an outer shell of chalcedony. Their size often reaches over a meter in diameter. Geodes made of dolomite and calcite have been found in sedimentary rocks in the Muswellbrook-Singleton region in New South Wales. According to the Australian Museum, volcanic geodes made of chalcedony, calcite, agate and amethyst quartz have been found in several regions in Queensland, New South Wales and Victoria.Learn more about Geology
Chert is most often created when microcrystals of silicon dioxide are formed within soft sediments that over time will turn into chalk or limestone. When large amounts of silicon dioxide microcrystals are present in the sediment, they start to clump together and can eventually form whole layers of chert within a limestone deposit.Full Answer >
Fossils form in sedimentary rocks such as limestone, shale and sandstone. The other two types of rock, igneous and metamorphic, form under conditions unsuitable for fossils.Full Answer >
Marble is a soft metamorphic rock that forms at the edges of tectonic plates, where limestone is exposed to regional metamorphism. The heat and pressure of the metamorphic zone force calcite inside the limestone to recrystallize and merge into the classic marble consistency.Full Answer >
Marble is a type of metamorphic rock found worldwide where geologic conditions are optimal to transform sedimentary carbonate stone such as limestone or dolomite. The mineral grains are recrystallized under substantial heat and pressure, creating white and colored crystalline rock that can be cut and highly polished.Full Answer >