Beenham meteorite, Union County, New Mexico, USAi

Regional Level Types
Beenham meteorite	Meteorite Fall Location
Union County	County
New Mexico	State
USA	Country

Ordinary chondrite, veined (L5,br)
Find, 1937; 44.4 kg

A number of masses and fragments were found. Remnants of fusion crust are still present in some instances. Inspections reveal chondrules and chondrule fragments of varying sizes and glass along with relatively equilibrated silicates within a brecciated, vein-rich grayish matrix. Compositionally, bulk iron contents (very roughly 15 wt% Fe), equilibrated olivine (Fa23.6), and low Ca-orthopyroxene are characteristic of the L-chondrite chemical group. Mineralogically, the meteorite consists primarily of olivine accompanied by both Ca-poor clinopyroxene and orthopyroxene plus smaller amounts of plagioclase (oligoclase). Minor troilite and Fe-Ni metal are also present in approximately equal proportions. Accessory chromite, ilmenite, merrillite, and isocubanite have also been reported. Strong mosaicism in olivine and twinned Ca-poor clinopyroxene [more abundant than orthopyroxene ('hypersthene')] and glass are due to shock effects. Multiple shock effects and movements in metal and troilite — Neumann lamellae in kamacite, twin lamellae in troilite, plessitic intergrowths — are detailed in Buseck (1967). Limonite stains are not uncommon.

A recent U-He age of ~1.59 Ga is reported. Combined with results from earlier K-Ar dating, these ages are believed to indicate a major collision involving an intermediate parent body (IPB) during the last one or two eons. Indeed, Buseck argues that the complex textures of metal-troilite interactions at the microscopic level are suggestive of several collisional events.

A single stone (original mass 4.2 kg) has been kept United States National Museum in Washington. A smaller moderate-sized mass is at Arizona State University [1.6384 kg in 2017].

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