Because the veins are massive but rare, traditional caving is often inefficient (as the veins are usually buried deep inside stone, not exposed to air).
Unlike most blocks, Corundum has a unique growth mechanic that allows it to be farmed sustainably: quark corundum farm
Place a 1 block above where the corundum will grow. It must be within 5 blocks of the basalt. Because the veins are massive but rare, traditional