The present invention relates to an X-ray amorphous-crystalline material with high solubility which can be used as a bioactive bone replacement material and as a substrate material in biotechnology. The new material comprising crystalline and X-ray amorphous phases is characterized in that according to .sup.31P-NMR measurements, it contains Q.sub.0-groups of orthophosphate and Q.sub.1-groups of diphosphate, the ortho-phosphates or Q.sub.0-groups making up 70 to 99.9% by weight relative to the total phosphorus content of the finished material and the diphosphates or Q.sub.1-groups making up 0.1 to 30% by weight relative to the total phosphorus content of the finished material, and that according to X-ray diffractometric measurements and relative to the total weight of the finished material, 30 to 99.9% by weight of a main crystal phase consisting of Ca.sub.2K.sub.1-xNa.sub.1+x(PO.sub.4).sub.2, where x=0.1 to 0.9, is contained in the bone replacement material and 0.1 to 20% by weight of a substance selected from the group consisting of Na.sub.2CaP.sub.2O.sub.7, K.sub.2CaP.sub.2O.sub.7, Ca.sub.2P.sub.2O.sub.7 and mixtures thereof is contained as a secondary crystal phase, the X-ray amorphous phases contained besides the main crystal phase jointly making up 0.1 to 70% by weight relative to the total weight of the finished material.