Analytical electron microscopy on individual grains from a portion of a chondritic interplanetary dust particle (aggregate W7029C1 from the NASA Johnson Space Center Cosmic Dust Collection) shows that layer silicate compose 50% of the silicate fraction examined. These layer silicates can be classified into two distinct crystallochemical groups: (1) fine-grained, polycrystalline smectite minerals, and (2) well-ordered, single crystals of kaolinite and Mg-poor talc. The layer silicates in the portion of sample W7029*A are dissimilar to those described in other chondritic porous aggregates. The predominant layer silicate assemblage in W7029*A indicates that heating of the aggregate during atmospheric entry was brief and probably to a temperature <300¿C. Comparison with terrestrial phyllosilicate occurrences suggests that some layer silicates in aggregate W7029*A may have been formed by alteration from preexisting silicate minerals at low temperatures (<25¿C) after aggregate formation.