  The prevalence of clouds in currently observable exoplanetary atmospheres
motivates the compilation and calculation of their optical properties. First,
we present a new open-source Mie scattering code known as LX-MIE, which is able
to consider large size parameters ($\sim 10^7$) using a single computational
treatment. We validate LX-MIE against the classical MIEV0 code as well as
previous studies. Second, we embark on an expanded survey of the published
literature for both the real and imaginary components of the refractive indices
of 32 condensate species. As much as possible, we rely on experimental
measurements of the refractive indices and resort to obtaining the real from
the imaginary component (or vice versa), via the Kramers-Kronig relation, only
in the absence of data. We use these refractive indices as input for LX-MIE to
compute the absorption, scattering and extinction efficiencies of all 32
condensate species. Finally, we use a three-parameter function to provide
convenient fits to the shape of the extinction efficiency curve. We show that
the errors associated with these simple fits in the Wide Field Camera 3 (WFC3),
J, H and K wavebands are $\sim 10\%$. These fits allow for the extinction cross
section or opacity of the condensate species to be easily included in retrieval
analyses of transmission spectra. We discuss prospects for future experimental
work. The compilation of the optical constants and LX-MIE are publicly
available as part of the open-source Exoclime Simulation Platform
(http://www.exoclime.org).
