Pholidostrophiid Brachiopods: Origin of the Nacreous Luster

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Science  07 Oct 1966:
Vol. 154, Issue 3745, pp. 153-155
DOI: 10.1126/science.154.3745.153


The "nacreous" luster characteristic of the pholidostrophiid group of fossil brachiopods results from a shell structure that produces superimposed sets of natural optical-diffraction gratings made of calcite. The wall structure is crossed lamellar, parallel to the shell surfdce; thus flakiness and development of reflecting surfaces are facilitated.