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Marlstone aggregate concretion, Sault Ste. Marie, Michigan, United States. A concretion is a hard, compact mass formed by the precipitation of mineral cement within the spaces between particles, and is found in sedimentary rock or soil. [1] Concretions are often ovoid or spherical in shape, although irregular shapes also occur.
- Formation and Appearance
- Composition
- Types of Concretions
Given their varied shapes, sizes, and compositions, concretions are often assumed to be dinosaur eggs, plant or animal fossils, or human artifacts. However, concretions are usually formed after sediment is buried but before it undergoes a physical change and becomes rock, which is a process called diagenesis. Concretions form when minerals precipit...
Concretions usually contain carbonate minerals such as calcite or iron oxide. However, others are composed of minerals like marcasite, dolomite, siderite, ankerite, pyrite, gypsum, and barite. A concretion contains one dominant mineral and several other minerals depending on the environmental conditions in which they are formed. For example, a carb...
Septarian Concretion
A septarian concretion is a type of concretion that contains angular cracks called "septaria." These cracks vary in shape, volume, and shrinkage. It is unclear what creates the septaria, but several mechanisms have been proposed, including the expansion of gases produced by decaying organic matter.
Cannonball Concretion
A cannonball concretion is a large spherical concretion that resembles a cannonball. This type of concretion can reach 3 m in diameter, and is often found along the Cannonball River in the US state of North Dakota. A cannonball concretion is formed by the early cementation of silt and sand by calcite.
Elongate Concretion
An elongate concretion forms parallel to sedimentary strata and has been studied extensively since it provides information on the orientation of fluid flow in the host rock. Other common types of concretions include hiatus concretions, Moqui Marbles, Kansas pop rocks, and calcium carbonate disc concretions.
concretion, mass or nodule of mineral matter, usually oval or nearly spherical in shape, and occurring in sedimentary rock. It is formed by the accumulation of mineral matter in the pore spaces of the sediment, usually around a fossil or fossil fragment acting as a nucleus.
Thunder eggs. Thunder eggs are spherical objects which form in some types of silica-rich volcanic rocks (e.g. rhyolites). As the volcanic lava cooled, trapped steam and other gases formed an expanding bubble. Silica and feldspar minerals often crystallise around the bubble or grow crystal fibres which radiate outwards from the its centre.
definition 3: a solid mass made by or as if by coalescence, such as a mass of calcium or other inorganic material found in living tissue, or a mineral mass found in sedimentary rock. related words:
Apr 3, 2020 · The size of the concretion may be related to the permeability of the rock in which it occurs: the more permeable the surrounding rock, the larger the concretion. Below we introduce the major types of concretions and similar rocks, as well as share images of concretions that were sent to us by the public and often initially mistaken for various types of fossils.
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Concretions. A concretion is a hard, compact mass of matter formed by the precipitation of mineral cement 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 derived from the Latin concretio " (act of ...
