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We present the most detailed data-driven exploration of cloud opacity in asubstellar object to-date. We have tested over 60 combinations of cloudcomposition and structure, particle size distribution, scattering model, andgas phase composition assumptions against archival $1-15 {\rm \mu m}$spectroscopy for the unusually red L4.5~dwarf 2MASSW~J2224438-015852 using theBrewster retrieval framework. We find that, within our framework, a model thatincludes enstatite and quartz cloud layers at shallow pressures, combined witha deep iron cloud deck fits the data best. This models assumes a Hansendistribution for particle sizes for each cloud, and Mie scattering. Weretrieved particle effective radii of $\log_{10} a {\rm (\mu m)} =-1.41^{+0.18}_{-0.17}$ for enstatite, $-0.44^{+0.04}_{-0.20}$ for quartz, and$-0.77^{+0.05}_{-0.06}$ for iron. Our inferred cloud column densities suggest${\rm (Mg/Si)} = 0.69^{+0.06}_{-0.08}$ if there are no other sinks formagnesium or silicon. Models that include forsterite alongside, or in place of,these cloud species are strongly rejected in favour of the above combination.We estimate a radius of $0.75 \pm 0.02$ Rjup, which is considerably smallerthan predicted by evolutionary models for a field age object with theluminosity of 2M2224-0158. Models which assume vertically constant gasfractions are consistently preferred over models that assume thermochemicalequilibrium. From our retrieved gas fractions we infer ${\rm [M/H]} =+0.38^{+0.07}_{-0.06}$ and ${\rm C/O} = 0.83^{+0.06}_{-0.07}$. Both thesevalues are towards the upper end of the stellar distribution in the Solarneighbourhood, and are mutually consistent in this context. A compositiontoward the extremes of the local distribution is consistent with this targetbeing an outlier in the ultracool dwarf population.

Cloud busting: enstatite and quartz clouds in the atmosphere of 2M2224-0158