In this investigation, three types of high alumina aggregates namely sillimanite, mullite and alumina rich aggregates were developed from sillimanite beach sand and calcined Al 2 O 3 by reaction sintering route. The various phases present in the sintered compacts were identified by X-ray diffraction study in conjunction with infrared study. Thermal shock behaviour of the aggregates with and without Fe 2 O 3 doping were measured by the room temperature flexural strength retention on ambient air quenching from 1000 o C against the number of cycles. The results obtained are presented and discussed in this paper. It was found that all Fe 2 O 3 containing samples show a strength enhancement on quenching by means of tempering. Attempts have been made to correlate this parameter with the microstructure and phase assembly of the product. (C)