Abstract Fe 3BO 6 can be an ideal compound for devising functional magnetic and dielectric properties in a single material for multiple applications such as electrodes, gas sensors, or medical tools. Useful to tailor such properties, here we report on a self-controlled Fe 3BO 6 growth in a specific shape of nanorods from a supercooled liquid precursor (an inorganic polymeric liquid or glass) of an initial composition (100 − x)B 2O 3 − xFe 2O 3, x = 40–50 mol%. B 2O 3 as a strong glass former co-bridges the Fe 3+ ions in oxygen polygons primarily in a 2-D interconnected polymer network so that it dictates preferably a 1-D directional growth on the reaction Fe 3+ species in form of a compound Fe 3BO 6, a favorable phase to nucleate and grow when annealing a precursor at 500–800 °C in ambient air. Distinct nanorods with a diameter ∼200 nm and 40–100 μm length have been formed on 10–15 min annealing a sample in microwave at moderate temperature 550 °C. A bonded surface B 2O 3 layer (15–25 nm thickness) has grown on the Fe 3BO 6 of the nanorods in situ in a specific structure. XPS bands in the Fe 3+, B 3+ and O 2− species confer this model structure. A local BO 3 → BO 4 conversion has incurred in the boroxol (B 3O 4.5) n , n → ∞, rings in the surface layer, showing three distinct IR bands at 1035, 1215 and 1425 cm −1.