One of our newest falls, Bilanga fell at 10:30 am local time October 27th, 1999, near the village of Bilanga Yanga in Gomponsago, Burkina Faso, Africa. The total weight is about 20 to 30 kg, including a 7.5 kg oriented mass. Bilanga is an very rare type of meteorite called a diogenite. "Diogenites are about as rare as aubrites with only fifteen known. They are almost pure orthopyroxene. The large crystals must have formed from cooling magma and accumulated on the bottom of the magma chamber. Like aubrites, diogenites are cumulates of mostly a single pure mineral. The large crystals mean that diogenites are plutonic; that is, they must have formed within their parent body under slowly cooling conditions, which allowed large crystals to form. They are the parent body's intrusive igneous rocks." edited quotes from "Rocks from Space" by O. Richard Norton.
Classification indicates that Bilanga is closely related to the Shalka, India diogenite. It has been suggested that similarities between Shalka, Tatahouine and the Bilanga diogenites make it likely that they were all ejected during the same event. However Bilanga looks very different from Tatahouine and is a different color than Shalka. One interesting thing about Bilanga is that is does have some free metal in it indicating the body it formed in was not completely differentiated. This is a very interesting meteorite.