Figure 10. Illustration of crystallite growth. (A) Scanning electron micrograph of synthetic hematite (α-Fe2O3) nanocrystals. The inset shows a photograph of macroscopic natural hematite crystals. (B) Scanning electron micrograph of synthetic aragonite (CaCO3) crystals. The inset shows a photograph of macroscopic natural aragonite crystals. As natural crystals typically start off as small crystallite nuclei that grow slowly under favorable conditions (chemical environment, temperature, and pressure), the existence of such large natural crystals illustrates the thermodynamic driving force behind crystallite growth.
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