  The lanthanide orthoborates, $Ln$BO$_3$, $Ln$ = Gd, Tb, Dy, Ho, Er, Yb
crystallise in a monoclinic structure with the magnetic $Ln^{3+}$ forming an
edge-sharing triangular lattice. The triangles are scalene, however all
deviations from the ideal equilateral geometry are less than 1.5%. The bulk
magnetic properties are studied using magnetic susceptibility, specific heat
and isothermal magnetisation measurements. Heat capacity measurements show
ordering features at $T \leq$ 2 K for $Ln$ = Gd, Tb, Dy, Er. No ordering is
observed for YbBO$_3$ at $T \geq$ 0.4 K and HoBO$_3$ is proposed to have a
non-magnetic singlet state. Isothermal magnetisation measurements indicate
isotropic Gd$^{3+}$ spins and strong single-ion anisotropy for the other
$Ln^{3+}$. The change in magnetic entropy has been evaluated to determine the
magnetocaloric effect in these materials. GdBO$_3$ and DyBO$_3$ are found to be
competitive magnetocaloric materials in the liquid helium temperature regime.
