Eucrite

Eucrite

[yoo-krahyt]

Eucrites are achondritic stony meteorites that originate from the surface of the asteroid 4 Vesta, and as such are part of the HED meteorite group. They are the most common achondrite group with well over 100 distinct finds at present.

Eucrites consist of basaltic rock from the crust of 4 Vesta. They are mostly composed of Ca-poor pyroxene, pigeonite, and Ca-rich plagioclase (anorthite).

Based on differences of chemical composition and features of the component crystals, they are subdivided into several groups:

  • Non-cumulate eucrites Are the most common variety and can be subdivided further:
    • Main series eucrites formed near the surface and are mostly, though not exclusively, regolith breccias lithified under the pressure of overlying newer deposits.
    • Stannern trend eucrites are a rare variety.
    • Nuevo Laredo trend eucrites are thought to come from deeper layers of 4 Vesta's crust, and are a transition group towards the cumulate eucrites.
  • Cumulate eucrites are rare types with oriented crystals, thought to have solidified in magma chambers deep within Vesta's crust.
  • Polymict eucrites are regolith breccias consisting of mostly eucrite fragments and less than one part in ten of diogenite, an arbitrary dividing line from the howardites, which are related in structure. They are comparably rare.

Eucrites are named from a Greek word meaning "easily distinguished".

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