Deterioration has been simulated in the laboratory for the fresh basalt samples from the Hittite site by cyclic wetting and drying, freezing and thawing, and salt crystallization. Comparison of decayed surfaces and fresh interiors of basalt samples have been made by x-ray powder diffraction, microscopic examination of thin-sections, infrared spectroscopy and transmission electron microscopy. Deterioration mechanisms have been explained in terms of changes observed in the original mineral constituents of basalts such as olivines, pyroxenes, and feldspars and in terms of clay mineral formation. Factors responsible for these types of deterioration are discussed.