The Kiglapait intrusion contains 330 ppm Sr and has Sr/Ca = 5 × 10 -3 and Rb/Sr = 3 × 10 -3, as determined by summation over the Layered Group of the intrusion. Wholerocks in the Lower Zone contain 403 FL0.141 ppm Sr, where FL is the fraction of liquid remaining; Sr drops to 180 ppm at the peak of augite production ( FL = 0.11) and rises to a maximum of 430 ppm in the Upper Zone before decreasing to 172 ppm at the end of crystallization. Feldspars in the Lower Zone contain 532 FL0.090 ppm Sr, increasing to 680 ppm in the Upper Zone before decreasing to 310 ppm at the end. Clinopyroxenes contain 15 to 30 ppm Sr and have a mineral-melt distribution coefficient D = 0.06 except near the top of the intrusion where D = 0.10. The calculated feldspar-liquid distribution coefficient has an average value near 1.75 but shows four distinct trends when plotted against XAn of feldspar. The first two of these are strongly correlated with the modal augite content of the liquid, on average by the relation D = 1.4 + 0.02 AugL. The third (decreasing) trend is due to co-crystallization of apatite, and the fourth (increasing) trend can best be attributed to a triclinic-monoclinic symmetry change in the feldspar at An 26, 1030°C. The compound feldspar-liquid distribution coefficient KD for Sr/Ca bears out these deductions in detail and yields ∆Gr for the Sr-Ca exchange ranging from nearly zero at the base of the Lower Zone to -26 k J/gramatom at the end of crystallization. The compound feldspar-liquid distribution coefficient KD for Rb/Sr varies from 0.3 in the Lower Zone to 1.1 at the end of crystallization. The ratio Ca F/Ca L is about 1.45 for troctolitic liquids containing 5% augite, for which KD (Sr-Ca) = 1.0 and DCa = DSr. For common basaltic liquids containing 20% augite, the Kiglapait data predict solSr F/Sr L = 1.8 , as commonly found elsewhere. The strong dependence of Dsr on augite content of the liquid illuminates the role of liquid composition and structure in determining the feldspar-liquid distribution coefficient. Conversely, a discontinuous change in the trend of DSr when apatite arrives shows that the effect is due to apatite crystallization itself, not to the continuous variation of the liquid as it becomes enriched in apatite component.