A school cafeteria was experiencing a strange growth near their dishwashing area. This off white coating would seem to grow with time. After the sample was examined with the Polarized Light Microscope, the sample was found not to be biological at all. The sample consisted of tiny elongated crystals. They were orthorhombic crystals with high birefringence when examined using crossed polarized light. The optical properties of the crystals indicated they were aragonite, which is a form of calcium carbonate. The hot and steamy conditions near their dishwashing station along with the right water conditions precipitated the calcium carbonate crystals.
To verify the results, a Nujol mull of the sample was made and analyzed by FTIR. The FTIR spectrum is matched to a standard spectrum below. The gray areas indicate where known peaks from the sample preparation procedure are located.
