It is included in the constituents of other crystals such as agate or calcite, domilat. Red and tan stones help the basal or root chakra, orange, sacral/spleen chakra, etc. It is what affects the metaphysical possibilities of these stones as well. It is due to the variety of clay, sand, organic residues, iron oxide and other materials. Its name is derived from the Greek word meaning egg.ĭifferent colours characterize oolites. These stones are mainly formed by grains such as rounded millet seeds, various microorganisms, corals or foraminifera, and skeletal fragments. 502-505.Oolite is a sedimentary rock formed in shallow, calm, warm marine waters. In: Encyclopedia of Sediments & Sedimentary Rocks (Ed. Lower Ordovician iron ooids and associated oolitic clays in Russia and Estonia: a clue to the origin of iron oolites? Sedimentary GeologyĤ. Modern iron ooids from a shallow-marine volcanic setting: Mahengetang, Indonesia Geologyģ. In: McGraw Hill Encyclopedia of Science & Technology, 10th Edition. Ooid sand from Stansbury Island, The Great Salt Lake. Ooid sand from Abu Dhabi, The United Arab Emirates. Width of view 18 mm.Ĭlose-up of oolite from Germany.
Width of sample 12 cm.Ĭlose-up of goethitic oolite from Germany. Oolite consisting of goethite (limonite) ooids from Germany. Jurassic Arab sequence in the Middle East, Smackover reservoir of the Gulf of Mexico, and several formations in the Anadarko and Appalachian basins among others are examples of oil reservoirs in oolitic limestones 4. Oolitic limestones form prolific oil reservoirs. Ooids occurring in Ordovician limestone in Estonia are strikingly similar in chemical composition, internal structures and REE (rare earth elements) distribution to modern iron-bearing ooids described from a vicinity of volcanically active island in Indonesia 3. Such ooids may form oolites which contain nothing but brown iron-rich ooids, but more commonly they occur within other sedimentary rocks. Concentric layering in iron-bearing ooids is thought to result from constant agitation of ooids associated with currents and expulsion of gas from the sediment 2. Iron-bearing goethitic (limonitic) ooids are probably formed out of volcanic pyroclastic (volcanic ash) material deposited in sea. Especially phosphatic and iron-bearing ooids composed of hematite and goethite seem to have been formed as such. Such ooids are formed by replacement of original calcium carbonate, but they may be also primary. Some ooids are made of silica ( chert), dolomite or fine-grained phosphatic material (collophane). Sometimes ooids form even in human-constructed features such as drainage pipes and water treatment plants 4. Even ooids made of evaporite minerals gypsum and halite have been reported 1. Some ooids form in fresh-water lakes, caves, caliche soils, hot springs, and rivers. Some ooids form in non-marine environments, the Great Salt Lake is probably the best known example of ooid formation in saline lake. Most modern ooids are composed of mineral aragonite. However, the exact formation mechanisms are still unresolved 4. It is believed that ooid formation is generally abiogenic process. Warm water is needed to lower the carbon dioxide content in water (higher temperature reduces the ability of water to keep gases dissolved) and thereby enhance the precipitation of calcium carbonate.
This is also the reason why ooids are so well-polished. Ooids are kept moving by waves which enables accretion to occur on all sides. Ooids in these places form a distinct type of sand - ooid sand.
Most ooids are marine, forming in shallow (less than 10 m, preferably even less than 2 meters), warm, and wave-agitated water such as the Persian Gulf and the Bahama Platform. Ooids may be spherical but some are elongated, depending on the shape of nucleus. Ooids usually possess a clearly developed growth banding. The terms “oolite” and “ooid” are derived from the Greek word for fish roe ( oon) which ooids resemble 4.
Oolite forms when ooids like this get cemented together. Ooid sand from Antelope Island, The Great Salt Lake. Larger grains with similar genesis are pisoids (pisoliths). The term “ooid” is applied to grains less than 2 mm in diameter. Nucleus is usually either mineral grain or biogenic fragment. Ooids are spheroidal grains with a nucleus and mineral cortex accreted around it which increases in sphericity with distance from the nucleus. Most oolites are limestones - ooids are made of calcium carbonate (minerals aragonite or calcite). Oolite is a sedimentary rock made up of ooids (ooliths) that are cemented together.
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