Lewis Cliff 87051 meteorite, Lewis Cliff, Buckley Island quadrangle, Transantarctic Mountains, Eastern Antarctica, Antarcticai

Regional Level Types
Lewis Cliff 87051 meteorite	Meteorite Fall Location
Lewis Cliff	Cliff
Buckley Island quadrangle	Quadrangle
Transantarctic Mountains	Mountain Range
Eastern Antarctica	Region
Antarctica	Continent

Angrite (basaltic achondrite)
Found 1987, 0.6 g

In the late 1980’s three small rocks were found in Antarctica which resembled the heretofore unique Angra Dos Reis (stone) meteorite which had fallen in 1868. The smallest of these new meteorites, Lewis Cliff 87051 (or, LEW 87051) is a single stone still covered with a fusion crust from its atmospheric entry. Its primary constituents are Olivine (~40%), Anorthitic Plagioclase (~34%), Fassaitic Pyroxene (20%), Kirschteinite (5%) and several minor components. Of course, Olivine, Plagioclase, and Pyroxene are commonly found in most chondritic and achondritic meteorites. While Olivine xenocrysts indicate that some impact mixing has occurred, the other equant Olivine crystals — intergrown with plagioclase and pyroxene — indicate that LEW 87051 is an igneously differentiated meteorite (achondrite). Bulk chemistry plus the presence of Fassaite, Ilmenite, and Kirschteinite are but the most obvious indicators that LEW 87051 is a geochemical relative of Angra dos Reis or, in modern parlance, an angrite.

The Angrites are characterized by low alkali contents, high Ca/Al ratios, and a distinctive mineral assemblage, generally including Al-Ca-Ti-rich pyroxene, Ca-rich plagioclase, and Ca-rich olivine that may have exsolved the mineral kirschsteinite. With the addition of recent finds from Antarctic, 22 stones — representing, perhaps, 13 or 14 separate meteorite falls — are now classified as Angrites. LEW 87051 itself is unusually similar to Asuka 881371, another small Antarctic angrite. All dated angrites are quite ancient with crystallization ages of ~ 4.6 billion years. LEW 87051, along with Angra dos Reis, appears to be slightly younger (~4.558 billion years) than a few angrites with crystallization ages of > 4.6 billion years. There has been some suggestions that the original parent body of the angrites may be (or was) as large as Vesta or even larger than Vesta. Vesta, almost certainly the parent body for most Howardites, Eucrites and Diogenites (HED meteorites), is the only large asteroid so far identified as the homeworld of a significant number of meteorites.

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