A new lithium borate Li3B5O8(OH)(2) (I), which is the enantiomer of the known Li3B5O8](OH)(2) (II), has been synthesized under mild hydrothermal conditions. Its crystal structure was determined from single crystal X-ray diffraction (XRD) data, further characterized by Fourier transform infrared (FT-IR) spectroscopy, Raman spectroscopy, XRD, differential thermal/thermogravimetric analysis (DTA-TG), and chemical analysis. It belongs to the tetragonal system, space group P4(3)2(1)2, with a = 6.8506(9) angstrom, c = 14.5601(15) angstrom, V = 683.32(15) angstrom(3), and Z = 4. Through an appropriate thermochemical cycle, the standard molar enthalpy of formation of LiB5O8(OH)(2) was determined to be -(4724.1 +/- 4.2) kJ . mol(-1) by solution calorimetry. Comparison of the experimental results with that of its enantiomer shows that the pair of enantiomers have the same standard molar enthalpy of formation like many other properties.