Bitburg—a group-IB iron meteorite with silicate inclusions

SUMMARY. Chemical and mineralogical investigations show that the Bitburg meteorite is not a pallasite, but a group-IB iron meteorite. Like other members of this group it contains chondritic silicates. THE Bitburg meteorite is the largest meteorite discovered in Europe. It was brought to scientific attention by Gibbs (I814), an American army officer who had seen it in 18o5. He removed some material from the surface of the meteorite, and some time later an unsuccessful attempt was made to smelt the 1.6 t mass. Most of the smelted material was thrown into the local mill channel, but of the order of 15 kg are preserved in meteorite collections around the world; 55 kg in the Geologische Landesanstalt in Berlin were lost during the 1939-45 war (G. Hoppe, priv. comm.). Very little unsmelted material is known. Brauns (192o) carried out a thorough search for the unsmelted material, and reported that it could be found as individual specimens in the Tiibingen, Berlin, and Vienna collections, the aggregate mass being only about 34 g. He observed that some unsmelted portions were remarkably different from others, and it now appears that at least one of these (the Tiibingen specimen) has been smelted. Bitburg is classified as a pallasite in Hey (I 966). This classification goes back to Rose (1863) and is apparently based on the identification of the silicates as olivine. Brezina (1885) created a special Albacher group of brecciated pallasites in which he placed Bitburg (under the synonymous name of Albacher Miihle) and Brenham. During a survey of the Ni, Ga, Ge, and Ir contents of metal-rich meteorites, we noted that the composition of a smelted Bitburg sample (Smithsonian Institution specimen NMNH 445) was distinctly different from that of any known pallasite, and relatively similar to that of the group-IB iron meteorites With silicate inclusions Woodbine and Pitts (group-IB consists of all meteorites listed as I-An2 in Wasson (197o) that have Ge concentrations lower than 19o ppm). The data are shown in Table I, together with those for Woodbine and Pitts and for the two most similar pallasites, Brenham and Eagle Station. The analytical techniques used are the same as those reported in Wasson (I97o).