Allende meteorite - CAI

What is Allende? 

A meteorite thin section from The Curchin Collection

The Allende meteorite is the largest known carbonaceous chondrite meteor to fall to Earth. Rocketing to Earth in the morning of February 8, 1969, the meteor generated enough light and sound to draw the attention of numerous onlookers across Northern Mexico and the Southwestern United States. The fireball eventually exploded into thousands of pieces, which fell across a vast expanse of land near the town of Pueblito de Allende in Chihuahua, Mexico.

Allende (its official name, by the way) is categorized as a CV3.2ox meteorite and is known for its abundance of high-temperature, refractory calcium-aluminum-rich inclusions (CAIs). Appearing as distinct white blebs in hand-sample, the CAIs have an enchanting history. 

Every CAI measured has the same age of ~4,568.2 Ma, meaning they represent the earliest solar system! They are composed of refractory minerals, such as melilite, anorthite, perovskite, and spinel, which form at very high temperatures, upwards of 1700K. What’s more is that they compositionally match the theoretical first condensates of the solar nebula. This is basically our sun’s composition, minus the hydrogen and helium.

Under the Microscope

The Allende design focuses on the CAI fine-grained minerals clustered as irregular shapes within a dark matrix of carbonaceous material. The muted appearance of these clusters in transmitted, cross-polarized light is an understatement to the wonders within. The design elements remain primitive and basic with occasional pops of color from surrounding chondrules.