NBS 18 , Calcite
Inorganic , Mineral
NBS 18 was prepared by I. Friedman, J. R. O’Neil and G. Cebula  of the U.S. Geological Survey. The material used for NBS 18 was a carbonatite from Fen, Norway, collected by B. Taylor, University of California, Davis, USA, and crushed by H. Friedrichsen, University of Tübingen, Federal Republic of Germany. The fraction between 88 μm and 440 μm was bottled as NBS 18. Its recommended δ13C value was determined in an international calibration study . The recommended δ18O value is a mean from data of several interlaboratory comparisons [1,3,4].
(R/I/C) Classification assigned to the property value for analyte (Recommended/Information/Certified)