H4 AND H5 CHONDRITES FROM THE RUBAL KHALI DESERT

Al-Jimshan is a highly weathered 11.45 kg chondrite that was found in 1955 in the Rub' al Khali Desert, Saudi Arabia (20-degrees-42'N, 52-de grees-50'E) about 240 km south-east of the town of al-Hadidah. The mai n mass is now at UCLA. Based on texture and mineral composition (olivi ne Fa17.7 +/- 0.4; pyroxene Fs15.7 +/- 1.0 Wo1.3 +/- 0.4), al-Jimshan is classified as an H4 chondrite of shock stage S2. The Bir-Hadi and a d-Dahbubah H chondrites, which also were found in the Rub' al Khali (H olm, 1962), are probably not paired with al-Jimshan. They are classifi ed as H5, shock stage S3 (Fa18.1 +/- 0.5, n = 10; Fs16.0 +/- 0.6 Wo1.1 +/- 0.4, n = 9) and H5, shock stage S2 (Fa17.9 +/- 0.3, n = 10; Fs15. 5 +/- 0.2 Wo1.0 +/- 0.4, n = 10), respectively.