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We investigate the structure of chiral nematic phases formed by colloidal suspensions of α-chitin rodlike particles in aqueous media. At sufficiently high volume fraction, owing to the particles anisotropic shape, a liquid-crystal phase appears that remarkably mimics the cholesteric geometry observed in biological tissues such as crustacean exoskeletons. The aim of the present work is to describe the structure of chitin colloidal dispersions and the chiral properties of the nematic phase. Both the pH and ionic strength affect the concentrations in the isotropic (C_I) and chiral nematic (C_N) phases at coexistence. The contribution of the crystallites to the ionic strength is evidenced by the linear variation of C_I and C_N with overall chitin volume fraction. When the ionic strength of the solution reaches about 10^-2 M, the system does not phase separate in bulk anymore; birefringent droplets form throughout the sample but do not …