The detrimental effects of ultrafine material in mineral processing circuits are well established: reduced grinding-mill energy efficiency, lower flotation recovery, and increased dewatering load, among others. For spodumene, the ultrafine fraction of concern is material finer than 20 µm, and is the major barrier to closing the gap between design and achieved lithium recoveries. The principal mechanism is behavioural: -20 µm spodumene particles exhibit markedly lower affinity for the fatty acid collector than the associated gangue, so they interfere with flotation rather than reporting cleanly to concentrate or tailings (Xu, 2017). Many operations pre-emptively deslime ahead of flotation, but this simply converts the interference problem into a direct loss, rejecting spodumene to the slimes stream (Cunningham, 2024). The only durable fix is to restrict the generation of -20 µm particles in the first place. Analysis of plant survey data from an operating spodumene concentrator indicates that roughly 75 80 per cent of all slimes are generated within the milling circuit itself, a consequence of poor undersize classification efficiency in the hydrocyclones closing the circuit: misplaced fines recirculate to the mill and are overground well past the size at which they were already liberated. This paper presents plant survey data from that spodumene concentrator and quantifies, through circuit simulation built on a mass- and energy-conserving relative-capacity model (Magdalinovic, 1991; Jankovic and Valery, 2013; Reja et al, 2023), the improvement available from replacing or supplementing cyclone classification with Derrick high-frequency fine screens. The simulation shows classification efficiency lifting from 46 per cent to 90 per cent (undersize basis), circulating load falling from 328 per cent to 134–175 per cent, and circuit capacity increasing by 10–22 per cent. The finer material reporting to the flotation feed is reduced due to reduced overgrinding. There are 14 per cent fewer fines at 100 microns and 48 per cent fewer fines at 25 microns; this is consistent with a 50 per cent reduction in true -20 µm ultrafine generation. Combined with the published linear relationship between mass rejected during desliming and lithium lost to slimes (Cunningham, 2024), this yields a modelled 30–50 per cent reduction in spodumene losses to slimes. The resulting recovery uplift gives a calculated payback of only 8 months. A documented copper cyclone-to-screen conversion at CIA Minera Condestable, Peru (Delgado, Diaz and Chambi, 2007; Dundar et al, 2014), against which the same capacity model was independently validated, is presented as field precedent for the same classification-efficiency mechanism. The advanced fine-screening technology has broader implications for mineral processing circuits generally, offering enhanced milling capacity, improved energy efficiency, and better flotation recovery together rather than as a trade-off.