Figure 1.

CaCO₃ crystals precipitated in the presence of Brilliant Blue R (BBR) and amino acids. a) Optical microscope and SEM images of calcite crystals precipitated in the presence of BBR and aspartic acid (Asp), as indicated. b) The structures of BBR and Asp. c) Colourless calcite rhombohedra and coloured vaterite crystals precipitated in the presence of BBR alone. d) Schematic diagrams showing the occlusion of BBR/amino acids within the equatorial zone. e) Calcite crystals grown in the presence of BBR and the amino acids glycine (Gly), glutamic acid (Glu), asparagine (Asn) and valine (Val) under conditions of [Ca²⁺]:[asp]:[dye]=250:25:1 and [Ca²⁺]:[Glu, Gly, Asn, Val]:[dye]=250:50:1.