[1][2] The element ratio corresponds to the oxide mixture Na2O·B2O3·4H2O, but the structure of the solid is quite different from that suggested by this formula.

Each sodium ion is surrounded by five oxygen atoms, in a square pyramid arrangement, at distances between 233 and 239 pm.

[2] The monoclinic form has been crystallized by mixing sodium hydroxide NaOH 14.5% (weight), boric acid H3BO3 9.0%, calcium hydroxide Ca(OH)2 10.7%, and water 65.8% and letting it stand for a long time at 293 K.[1] The orthorhombic form has been crystallized, as thin needles, from a solution of sodium hydroxide and boric acid at pH 12 (which meant a boron to sodium mole ratio of 3:2 in the solution), left to evaporate at room temperature.

[2] The starting solution for evaporative crystallization can be prepared also from sodium metaborate tetrahydrate NaBO2·4H2O.

[2] The crystallization process has been studied by Raman spectroscopy of nanometre-size droplets of solution as the water evaporates in air.