| 02 Jul 2026
George Perkins Merrill's Analyses of Chondrules and Chondritic Meteorites
Abstract. George Perkins Merrill (1854–1929) was the preeminent American meteoriticist of the first quarter of the 20th Century. He applied to that science his pioneering knowledge and skill in the petrographic analysis of chondritic meteorites. Throughout his long and distinguished career with the United States National Museum, now the Smithsonian Institution of Washington, D.C., Merrill authored over seventy publications on meteorites. While many of those contributions described new irons and stones which had come into the museum’s collection, a pair of papers concerning the origin of chondrules and the evidence for and causes of metamorphism of chondritic meteorites led directly to his selection as the second recipient of the J. Lawrence Smith Medal which was awarded by the National Academy of Sciences in 1922 for outstanding accomplishments in the study of meteorites. The origins, primary arguments, and subsequent reception of those two landmark papers are herein reviewed. Particular attention is given to how Merrill’s hypotheses on chondrule formation and the evidence for thermal and dynamic metamorphic alteration of chondrites have come to underpin and advanced modern understandings of the early history of the solar system.
I received the following input from Professor Alan Rubin via email after I pointed him to this open source review process. I will, of course, fully address these extremely helpful comment.
Thanks for steering me toward your paper on George Merrill. I am frequently reminded of him when I encounter his eponymous mineral in chondrites. I have a few comments on this manuscript as well. Line
165: Anorthite is very rare in chondrules from type-3 chondrites. It really only shows up in grains >2 um in chondrites of type 5 and 6 (where the grains can exceed 50 um). Line 170. Radial pyroxene chondrules constitute about 8% of the chondrules in ordinary chondrites. Line 210. Compound chondrules are not equivalent to porphyritic chondrules. Most chondrules are porphyritic, so most compound chondrules are porphyritic as well. But, other chondrule textural types can form compound chondrules as well. We discussed this in a 1995 paper by Wasson et al. Line 323: not not hot. Line 575:
I'm not sure exactly what you are referring to as a marginal rind. It could be a bleached zone around many nonporphyritic chondrules due to parent-body aqueous alteration, or it could just be a thin fine-grained matrix-like rim around many chondrules in type-3 chondrites. Line 639: Interestingly, FeCl, lawrencite, is a primary phase (albeit a rare one) in enstatite chondrites.
I also want to note that some type-3 ordinary chondrites contain large irregular fragments of porphyritic chondrules that Bob Dodd first made me aware of. These have textures essentially identical to normal-size porphyritic chondrules and are likely just chondrule fragments, plausibly broken in the regolith prior to final whole-rock consolidation. I found that porphyritic chondrules are particularly friable when I tried to exhume them from their adhering matrix. This is the reason that many compositional studies of separated chondrules have much larger proportions of nonporphyritic samples. It is a selection effect of excavation.
Finally, I was a little surprised you did not cite John Burke's masterful 1986 work Cosmic Debris which is a fine study of the history of meteoritics.