A new series of mixed borates of rare-earth elements and calcium with the composition R2CaB10O19 (where R represents rare-earth element) has been identified in the system R2O3-CaO-B2O3. These isostructural compounds exhibit a powder second harmonic generation (SHG) effect about twice larger than that of KDP (KH2PO4). The crystal structure of La2CaB10O19 (LCB), one member of the RCB family, has been determined by single crystal X-ray diffraction analysis. The compound crystallizes in the monoclinic system, space group C2, with a equals 11.043(3)angstrom, b equals 6.563(2)angstrom, c equals 9.129(2)angstrom, (alpha) equals (gamma) equals 90 degrees, (beta) equals 91.47 degrees, and two formula units per cell. LCB melts congruently with a melting point of 1065 plus or minus 2 degrees Celsius. Single crystals of LCB and Nd doped LCB in centimeter size have been grown from the stoichiometric melt. The preliminary results on properties of LCB are presented.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.