Zacatecas (1792) meteorite, Vetagrande Municipality, Zacatecas, Mexicoi

Regional Level Types
Zacatecas (1792) meteorite	Meteorite Fall Location
Vetagrande Municipality	Municipality
Zacatecas	State
Mexico	Country

Iron meteorite (Iron, ungrouped)
Find, 1792; 1 ton

The Zacatecas (1792) iron meteorite mass [an irregular 106x56x30 cm block] was apparently known to some of the conquistadores by the 16th century, but only in the early 19th century was its presence publicized with several samples being sent to Europe and elsewhere. Most of the currently held mass is held at the Old School of Engineering in Mexico City (~780 kg), but Buchwald (1975) has argued persuasively that the original mass would have been ~1 ton. The meteorite (Ni ~6%) consists primarily of polycrystalline kamacite with accessory troilite, schreibersite, and chromite. Some of the troilite has been shock-melted. The meteorite possesses indistinct Widmanstätten patterns. These unusual are indicative of an incomplete conversion of the original high-temperature taenite phase into the more uniform kamacite-dominated octahedral pattern found in most irons with this composition.

117 ungrouped iron meteorites (~10% of all irons) are currently listed with the Meteoritical Bulletin Database (August 2015). Zacatecas (1792) is the 5th most massive member of this group. Please note, 'ungrouped' is not a synonym for 'unclassified.' An 'ungrouped' iron has been classified — and it does not belong to any of the defined iron meteorite groups.

What's in a name? Zacatecas (1969) is a much less massive 6.69 kg IIIAB iron found much more recently in the same general area.

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References