for quantitative analysis. He pursued his petrographic research on 

 igneous and metamorphic rocks of an area in northeast Vermont. 

 Albert W. Forslev, Associate Curator of Mineralogy, began a com- 

 prehensive investigation of the mechanical, chemical, and min- 

 eralogical properties of sediments and sedimentary rocks to gain 

 information on factors affecting the stability of minerals in sedi- 

 ments, the rearrangement of constituent minerals during the con- 

 solidation and low-grade metamorphism, and the formation of clay 

 minerals. The reported occurrence in Arizona of ecdemite, a rare 

 oxychloride of lead and arsenic, drew his attention. Doubtful of 

 the report of the occurrence, he obtained some twenty specimens, all 

 supposedly ecdemite, from various collectors in the Southwest. 

 Careful study and X-ray analysis of the specimens confirmed his 

 doubt. All proved to be mimetite, a more common mineral similar 

 in composition to ecdemite. The X-ray diffraction equipment of 

 the William J. and Joan A. Chalmers Mineralogical Laboratory was 

 in almost constant use during the year for the identification of many 

 unusual minerals obtained by the Museum. 



Dr. Sharat K. Roy, Chief Curator of Geology, returned to his 

 duties after a year's stay abroad, where he was engaged in research 

 and consultation on stony meteorites, especially concentrating on 

 those that contained certain rounded grains called chondrules. 

 Believing that chondrules, the like of which, structurally or in manner 

 of crystallization, have not been observed in terrestrial rocks, may 

 hold the key to the origin of meteorites at large. Chief Curator Roy 

 set out to examine petrographically as many thin sections of chon- 

 dritic meteorites as he could. During this examination he noted the 

 order in which the different minerals have appeared and the degree 

 of metamorphism they have undergone. He also noted the textural 

 and structural variations and the distribution and interrelationships 

 of the various components of the chondrules. The petrographic 

 study was supplemented by microphotographs of thin sections, 

 both in color and black-and-white, taken to provide the necessary 

 information for interpretation of the features observed under the 

 microscope and as a reference for comparison. 



It is hoped that the knowledge gained by this critical study of 

 chondrules will remove certain existing uncertainties and help build 

 an acceptable theory of their origin and development. Dr. Roy 

 wishes to express his grateful appreciation for the research grant he 

 received from the National Science Foundation to pursue the study. 

 He also wishes to extend his hearty thanks for the cordial co-opera- 

 tion and use of laboratory facilities given him by the various institu- 

 tions he visited in Europe and India. 



61 



