The lattice parameters of kaliborite, HKMg₂B₁₂O₁₆(OH)₁₀·4H₂O, were determined from photographs and diffractomer data: $a = 18.53 \pm 0.03$Å, $b = 8.43 \pm 0.02$Å, $c = 14.665 \pm 0.007$Å, $\beta = 100.13° \pm 0.12°$. The space group is C 2/c, monoclinic. Oxygen and boron atoms are arranged into compex ions $[B_{6}O_{8}(OH)_{5}]_{n}^{-3n}$, linked to each other along the b axis by alternating BO₄ tetrahedra and BO₃ triangles. The Mg atoms are 6-coordinated according to an octahedron, and the K atoms have a cubic distorted coordination. These cations form the bridges among the boron-oxygen chains. At this stage of work the reliability index R is 15%.