A central question to understanding biomineralization is determining how bimolecules are integrated within inorganic host lattices, thereby changing material properties yet retaining single crystal structure of the biomineral. We have addressed guest incorporation within single biomineral crystals by investigating face specificity, anisotropy and the role of charges in fluorescent calcium oxalate monohydrate (COM) crystals nucleated from solutions containing eosin Y, fluoresceins and rhodamines. Additionally, we have examined the specificity of incorporation of Protein G wild-type (G-wt) and its mutant (G-Delta6, in which four aspartic acids and two glutamic acids have been replaced by the corresponding asparagine or glutamine), where G-wt promotes and G-Delta6 inhibits COM crystal growth. We found that (1) the negatively charged fluorophores, as well as the fluorophore-labeled proteins, G-wt and G-Delta6, were successfully incorporated during growth into the same {101} growth sectors in preference to all others, (2) the positively charged TRITC (tetramethyl rhodamine isothiocyanate) was not incorporated as free fluorophore, but it became incorporated if conjugated to G-wt and G-Delta6; (3) once the fluorophores are incorporated, the polarization measurements of adsorption and emission were similar irrespectively whether taken from COM containing the free fluorophores, or the protein conjugates. The anisotropy was similar for rhodamines and fluoresceins.