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Martian Meteorites | Lunar Rocks | HED Group | PAC Group | Carbonaceous Chondrites | Rare Chondrites Last Updated: 15 October 2014

Angrites

The achondrites of this group are named for their type specimen, Angra dos Reis, a meteorite that fell in Rio de Janeiro, Brazil, in early 1869. Angra dos Reis is a unique igneous rock that is largely composed of the rare pyroxene fassaite, an aluminium-titanium diopside. During the last two decades, a handful of similar fassaite-rich meteorites have been recovered, leading to the establishment of the angrite group, presently comprising six members.

The angrites are primarily composed of varying amounts of fassaitic pyroxene, anorthitic plagioclase, minor olivine, kirschsteinite, along with other accessory minerals and phases. They are basaltic rocks with cumulate textures, often containing porous areas and abundant round vesicles with diameters up to 2.5 cm. These vesicles have been interpreted as remnants of gas-bubbles that formed prior to the crystallization of the rock. However, current research suggests that the vesicles originally were solid spheres that have been exsolved in subsequent stages of rock-formation. Both theories are consistent with a magmatic origin of the angrites, making them the most ancient igneous rocks known. They show crystallization ages of ~ 4.55 billion years, which suggests their formation occurred in the early days of the unfolding solar system. The angrites are thought to have formed on one of the earliest differentiated asteroids from the igneous processing of CAI-rich chondritic matter, similar to carbonaceous chondrites of the CI or CM group.

By comparing the reflectance spectra of the angrites to that of several main belt asteroids, two analogs were identified - 289 Nenetta, and 3819 Robinson. Further research will determine whether one of these asteroids actually represents the angrite parent body. Only three angrites are currently available to the private collector; these are Sahara 99555, a single stone that was found in the Sahara desert in 1999,  D'Orbigny, an Argentinian find from 1979 that wasn't recognized as a meteorite until 1998 and NWA 1670 with a total weight of only 30gr.... 

 

NWA 1670 Angrite

Found : 2001 in occidental sahara, 

TKW : 30.6 gr 

Nwa 1670 is unique compare to the other angrites: it's highly shocked,
it has big olivine xenocrysts and it is the most magnesian olivine among all the known angrites.
See publication from Tokyo University and NASA:
NORTHWEST AFRICA 1670: A NEW QUENCHED ANGRITE.
A DISSOLVED OLIVINE XENOCRYST COMPONENT IN THE ANGRITE MAGMA.

 

NWA 1670-00

2.80 gr

Full slice of angrite !

$ price on request

NWA 1670-01

0.136 gr !

Very thin and nice slice !

Sold

NWA 1670-02

0.102 gr !

Very thin and nice slice ! SOLD

$ 285

NWA 1670-01

0.131 gr !

Two thin slice of this rare type !

Sold

 

 

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