Mineralogy of a calcite sputum lith

A rare case of calcite sputum lith coughed up from the bronchus of a 38-yr-old male subject has been investigated mineralogically. The sputum liths are milky white, sandy grains of 1-3mm in size with “confetto”-like appearance. Under the polarized microscope, they make polycrystalline aggregate. According to the microdiffractometric as well as x-ray microprobe analytic investigation, the mineral has been proved to be almost pure calcite composed of (Ca0.97-0.98Mg0.03-0.02)CO3 with slight compositional zoning. The P-content is only traceable. So any contribution from bone material may be scarecely conceivable. The genetic origin of sputum lith is still remains unknown.