A Classification for the Yamato-74 Chondrites Based on the Chemical Composition of their Olivines and Pyroxenes

Electron microprobe studies have been made of olivines and pyroxenes in thirty three Yamato chondrites collected in Antarctica in 1974,together with two chondrites collected in 1975 and two Mt. Baldr chondrites. The small fragments used for the analyses were so chipped from the meteorites that contamination to the original materials is minimal. On the basis of histograms of iron contents of olivines and orthopyroxenes, the following chondrites have been identified : 4 unequilibrated chondrites; 8 H type, 2 L type and 1 LL type moderately equilibrated ones; and 12 H type, 9 L type and 1 LL type equilibrated chondrite. Absence of the E type chondrite and predominance of the H type ones are notable features but may not be significant at this stage of identification.