| Abstract: | Estimates of the volume percents of chondrules in petrographic thin sections are notoriously unreliable, ranging widely among different observers for the same meteorite or even for the same thin section. The set of visual-estimation guides presented herein should help narrow the uncertainties in such estimates and lead to a more consistent picture of chondrule abundances than is now apparent from the literature. In generating this set of guides other quantitative measures were also retained and examined. First, the expected error in the volume abundance of chondrules, due solely to sampling of homogeneous rocks by random thin sections, decreases as the inverse of the volume abundance of the chondrules. Second, our experiments of “softly” settled chondrules could not exceed chondrule abundances of 60 vol %. If chondrule-bearing rocks are found to exceed this value, the physical environment where they accreted must have had a greater gravity field than is available on asteroid-size bodies. |
