OoidOoids (, from Ancient Greek (ōión)'egg stone') are small (commonly ≤2 mm in diameter), spheroidal, "coated" (layered) sedimentary grains, usually composed of calcium carbonate, but sometimes made up of iron- or phosphate-based minerals. Ooids usually form on the sea floor, most commonly in shallow tropical seas (around the Bahamas, for example, or in the Persian Gulf).
Calcium carbonateChemical compoundChemical compoundCrystal structure of calciteCalcium carbonate is a chemical compound with the chemical formulaCaCO3. It is a common substance found in rocks as the mineralscalcite and aragonite, most notably in chalk and limestone, eggshells, gastropod shells, shellfish skeletons and pearls. Materials containing much calcium carbonate or resembling it are described as calcareous. Calcium carbonate is the active ingredient in agricultural lime.
LimoniteLimonite () is an iron ore consisting of a mixture of hydratediron(III) oxide-hydroxides in varying composition. The generic formula is frequently written as FeO(OH)·nH2O, although this is not entirely accurate as the ratio of oxide to hydroxide can vary quite widely. Limonite is one of the three principal iron ores, the others being hematite and magnetite, and has been mined for the production of iron since at least 400 BC.
Sedimentary rockSedimentary rocks are types of rock formed by the cementation of sediments—i.e. particles made of minerals (geological detritus) or organic matter (biological detritus)—that have been accumulated or deposited at Earth's surface. Sedimentation is any process that causes these particles to settle in place. Geological detritus originates from weathering and erosion of existing rocks, or from the solidification of molten lava blobs erupted by volcanoes.
SideriteSiderite is a mineral composed of iron(II) carbonate (FeCO3). Its name comes from the Ancient Greek word (sídēros), meaning "iron". A valuable iron ore, it consists of 48% iron and lacks sulfur and phosphorus. Zinc, magnesium, and manganese commonly substitute for the iron, resulting in the siderite-smithsonite, siderite-magnesite, and siderite-rhodochrositesolid solution series.
ConcretionA concretion is a hard and compact mass formed by the precipitation of mineralcement within the spaces between particles, and is found in sedimentary rock or soil. Concretions are often ovoid or spherical in shape, although irregular shapes also occur. The word concretion is borrowed from Latinconcretio'(act of) compacting, condensing, congealing, uniting', itself derived from concrescere'to thicken, condense, congeal', from con-'together' and crescere'to grow'.
BauxiteBauxite ( ) is a sedimentary rock with a relatively high aluminium content. It is the world's main source of aluminium and gallium. Bauxite consists mostly of the aluminium minerals gibbsite (Al(OH)3), boehmite (γ-AlO(OH)), and diaspore (α-AlO(OH)), mixed with the two iron oxides goethite (FeO(OH)) and hematite (Fe2O3), the aluminium clay mineral kaolinite (Al2Si2O5(OH)4) and small amounts of anatase (TiO2) and ilmenite (FeTiO3 or FeO·TiO2).
SpheroidA spheroid, also known as an ellipsoid of revolution or rotational ellipsoid, is a quadricsurface obtained by rotating an ellipse about one of its principal axes; in other words, an ellipsoid with two equal semi-diameters. A spheroid has circular symmetry. If the ellipse is rotated about its major axis, the result is a prolate spheroid, elongated like a rugby ball. The American football is similar but has a pointier end than a spheroid could.
Ancient GreekAncient Greek (Ἑλληνική, Hellēnikḗ [hellɛːnikɛ̌ː]) includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (c. 1400 – c. 1200 BC), Dark Ages (c. 1200 – c. 800 BC), the Archaic or Homeric period (c. 800 – c. 500 BC), and the Classical period (c. 500 – c. 300 BC).
PeaPea is a pulse or fodder crop, but the word often refers to the seed or sometimes the pod of this flowering plant species. Peas are eaten as a vegetable. Carl Linnaeus gave the species the scientific name Pisum sativum in 1753 (meaning cultivated pea). Some sources now treat it as Lathyrus oleraceus; however the need and justification for the change is disputed.
OoliteOolite or oölite (from Ancient Greek ᾠόν (ōión) 'egg stone') is a sedimentary rock formed from ooids, spherical grains composed of concentric layers. Strictly, oolites consist of ooids of diameter 0.25–2 millimetres; rocks composed of ooids larger than 2 mm are called pisolites. The term oolith can refer to oolite or individual ooids.MicrospheruliteMicrospherulites are microscopic spherical particles with diameter less than two mm, usually in the 100 micrometre range, mainly consisting of mineral material (the Greek litos means "stone"). Only bodies created by natural physico-chemical processes, with no contribution of either biological (in aqueous sedimentary environments this contribution is possible) or human activity, are considered to be microspherulites.
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