Nagy et al. : Environment of Orgueil Meteorite Parent Body 545 



Magnetite (Fe304) is a component in Orgueil;* the magnetite lines were 

 sharp enough to ensure that they were not caused by chromite (FeCr204), 

 which gives a similar pattern. The 2.97 A, 2.53 A, 1.71 A, and 1.62 A magnetite 

 hnes were recorded. Chromite peaks at 4.83 A and 1.91 A were not observed; 

 the strongest diffraction effect was sharp and always appeared at 2.53 A. The 

 x-ray diffraction patterns showed no evidence for hematite (a-Fe203), pyrite 

 (FeS2), troilite (FeS), pyrrhotite (FeySs), metallic iron and nickel, fayalite 

 (Fe2Si04), forsterite (Mg2Si04), enstatite (MgSiOs), or gibbsite (Alo03-3H20) 

 in Orgueil. The X-ray data indicated that the mineral composition of the 

 sample was heterogeneous to some extent. 



The water soluble salt was obtained by heating the sample in water in sealed 

 glass tubes at 104° C. for a period of 2 days, after which the supernatant liquid 

 was poured off, filtered, and evaporated. The crystalline product was MgS04- 

 6H2O; there were a few minor peaks which have not been identified. The 

 diffraction patterns showed that subjecting the Orgueil sample to rapid heating 

 (6.5° C. per minute) to 980° C. temperature in air, led to the formation of a 

 limited cjuantity of olivine (forsterite) and hematite. When the chlorite and 

 the serpentine standards were subjected to the identical heat treatment they 

 seem to have fully recrystallized into the high temperature minerals. 



The diffraction pattern of Ivuna was almost identical to Orgueil, but Murray 

 showed signs of containing olivine. The diffraction patterns of the noncarbona- 

 ceous chondrites were sharp and distinct; the results were in agreement with 

 published data. 



Electron diffraction studies were conducted in an attempt to confirm the 

 x-ray data. Specimens were prepared by dusting with a Q-tip because it was 

 thought that this method would lead to a random orientation of the flakes. 

 Patterns were taken in selected areas and in manipulator positions. A "beam- 

 stop" was used for some patterns; the centers of the patterns were reduced with 

 Farmer's reducer. Measurements were made both on plates and on enlarge- 

 ments. 



The electron diffraction diagrams showed a series of concentric rings, with a 

 hexagonal (or pseudohexagonal) array of spots overimposed on most rings. 

 There were also 2 diffuse bands present. 001 reflections were not recorded. 



The electron and X-ray diffraction data were in good agreement (d-values in 

 TABLE 4 are based on both). There were only two differences. Electron 

 diffraction diagrams did not show magnetite lines (probably because of the 

 scarcity of magnetite in the fields that were examined). Furthermore, electron 

 diffraction diagrams were always sharp and distinct. The hexagonal pattern 

 of spots was related apparently to diffractions from the basic hexagonal building 

 units of layer silicate structures. 



Thermogravimetric A nalysis 



In addition to the X-ray and electron diffraction methods, there are 2 thermal 

 methods of layer lattice silicate analysis: differential thermal analysis and 

 thermogravimetric analysis. Faust^- obtained differential thermal curves on 

 Orgueil and Mighei but was unable to interpret the data because of the inter- 



* Part of the magnetite may contain Ni, as NiFe204 . 



