Mesa La Caguama        27°35’N, 113°4’W

Baja California Sur, Mexico

Find: 1971

Classification: Iron meteorite (IAB-MG)

History: An "extremely heavy rock" was found by Francisco Arce Arce in 1971. It was discovered along a burro trail between Rancho San Gregorio and the dirt road that leads to Rancho San Francisco, off the paved road to San Ignacio. Noting the unusual density of the rock, Mr. Arce Arce believed that it might be something special. In 1991, Richard and Alice Gross were revisiting the area after an earlier tour, were shown the object, and, on a later trip in 2003, brought it to the US in the hope of confirming its extraterrestrial nature, and to sell it on behalf of Mr. Arce Arce. The specimen was brought to Michael Blood, who brokered the sale of the iron to the Utas Meteorite Collection.

Physical characteristics: The meteorite weighed 6897 g when found. The flattened, irregular mass is differentially weathered due to its position in the ground: one side of the iron is relatively smooth, while the other exhibits numerous larger, more sharply defined regmaglypts. Several of the promontories show crude saw and hammer marks: evidence of failed attempts to remove samples. Two ~1-2 cm. sulfide inclusions are visible on the surface of the iron.

Petrography: (J.T. Wasson, UCLA) Relatively fresh iron. Few inclusions; one phosphide 1.5 × 0.2 mm, a few smaller ones. Kamacite bandwidth is 1.8±0.3 mm, thus Og. A 1-2 mm-thick heat-altered rim is visible along one edge of the cut face.

Geochemistry: Composition: 4.59 mg/g Co, 68.6 mg/g Ni, 94.3 μg/g Ga, 473 μg/g Ge, 10.3 μg/g As, 2.16 μg/g Ir, and 1.431 μg/g Au. Based on the composition and structure, this a member of the IAB main group. It falls near the low-Au end of the group. Its nearest relatives are Allan Hills 76002, Cosby's Creek, Morasko, and New Leipzig, but it is compositionally resolved from all of these.

Classification: Iron, IAB-MG

Specimens: Only one specimen known.