The type I carbonaceous chondrites, with volatiles between 24 and 30% (at 1000 C, N2 atm.), contain the maximum percentage of the low-temperature ground mass, in which the high-temperature minerals are dispersed as ‘microchondrules’. In the type II carbonaceous chondrites (vol. 12–24%), the loosely cohering aggregates of microchondrules, ‘grape-bunch chondrules’, reach a maximum. The type III carbonaceous chondrites and some enstatite chondrites (vol. 2–12%) contain the maximum of the ‘partly coalesced chondrules’, in which microchondrules of olivine and nickel-iron appear. The ureilites are interpreted as impact shocked aggregates of microchondrules in differing states of coalescence. The ‘fully coalesced chondrules’ are characteristic for the ordinary chondrites with volatiles below 1%.