Ohio Shale concretions are composed primarily of carbonate (limestone or dolomite) rock and are enclosed within a dark-gray to black shale. They have been likened to "marbles pressed within the pages of a book," because the horizontally bedded shale bends around the concretion, both above and below. They range in diam-eter from a few inches to more than 9 feet, but most are less than 6.
Ironstone Concretion is the name used in the collectible stone industry for concretions of iron oxide and sandstone. These stones are rarely polished or treated and are sold in their natural form as roundish, gray, golf. Iron-oxide nodules or concretions are the most common kind of meteorwrong sent to us.
Hematite and magnetite are two common iron-oxide minerals, but the discussion here applies to related minerals such as limonite and goethite. Most iron ore deposits consist mainly of hematite, magnetite, or both. Iron-oxide concretions, iron-oxide nodules, and ironstones are often mistaken for meteorites.
IRON OXIDE CONCRETIONS The majority of interesting iron oxide (ironstone) concretions occur close to the base of the Cretaceous rock series, near their contact with the Cambrian metasedimentary rocks or Silurian granodiorite. Discover the fascinating formation and processes behind ironstone concretions, unraveling their geological mysteries and significance. About Ironstone concretion Hide A concretion cemented by iron oxide/hydroxide/carbonate minerals.
Hey all, I recently received a piece of shale from the Cleveland Shale in Ohio with what appears to be an ironstone concretion inside it. It appears on both the top and bottom of the piece of shale from what I can see and is 2 x 2 inches. There's also a small circular depression around the concre.
This rock consists of over a dozen small to medium-sized, subspherical ironstone nodules (= iron oxide rock). They have become cemented together by a crust of the same iron oxide material. This entry was posted in #geoblog, GeoPic of the Week, More Views, Sedimentary Features and tagged Arkansas, concretions, leisegang, rock collection, sandstone pipes, Septarian concretion on November 6, 2015.
← Geopic of the week: Biotite crystal from Magnet Cove More views of Arkansas Bauxite →. Iron oxide concretions are formed from post depositional, paleogroundwater chemical interaction with iron minerals in porous sedimentary rocks. The concretions record a history of iron mobilization and precipitation caused by changes in pH, oxidation conditions, and activity of bacteria.
Transport limited growth rates may be used to estimate the duration of fluid flow events. The Jurassic.
