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Dendrite (crystal): Wikis

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Manganese dendrites on a limestone bedding plane from Solingen, Germany. Scale in mm.

A crystal dendrite is a crystal that develops with a typical multi-branching tree-like form. Dendritic crystal growth is very common and illustrated by snowflake formation and frost patterns on a window. Dendritic crystallization forms a natural fractal pattern.

The term "dendrite" comes from the Greek word dendron, which means "tree".

Contents

Mineralogy and paleontology

Example of a dendrite on pyrolusite.

In paleontology, dendritic mineral crystal forms are often mistaken for fossils. These pseudofossils form as naturally occurring fissures in the rock are filled by percolating mineral solutions. They form when water rich in manganese and iron flows along fractures and bedding planes between layers of limestone and other rock types, depositing dendritic crystals as the solution flows through. A variety of manganese oxides and hydroxides are involved, including:

  • birnessite (Na4Mn14O27·9H2O)
  • coronadite (PbMn8O16)
  • cryptomelane (KMn8O16)
  • hollandite (BaMn8O16)
  • romanechite ((Ba,H2O)Mn5O10)
  • todorokite ((Ba,Mn,Mg,Ca,K,Na)2Mn3O12·3H2O) and others.

A three-dimensional form of dendrite develops in fissures in quartz, forming moss agate.

Crystallography and metallurgy

a silver crystal, electrolytic refined with visible dendritic structures.

In chemistry, a dendrite is a crystal that branches into two parts during growth.

NASA microgravity experiment

Animated GIF of dendrite formation - NASA

The Isothermal Dendritic Growth Experiment (IDGE) is a materials science solidification experiment that researchers use on Space Shuttle missions to investigate dendritic growth. Dendritic solidification is one of the most common forms of solidifying metals and alloys. When materials crystallize or solidify under certain conditions, they freeze unstably, resulting in dendritic forms. Scientists are particularly interested in dendrite size, shape, and how the branches of the dendrites interact with each other. These characteristics largely determine the properties of the material.

See also

References


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