Figure F9. CaCO3 calculated from Ca determined by ICP-AES vs. CaCO3 determined by coulometer. Scatter seen for measured vs. calculated CaCO3 > ~75 wt% is attributable to a combination of two factors: (1) precision for Ca determined by ICP-AES is relatively low (11.5%) and (2) some samples analyzed (e.g., Oligocene carbonate ooze and chalk) contain more CaCO3 than the ICP-AES standard with highest CaCO3 content (NIST-IC, an argillaceous limestone containing 90 wt% CaCO3; 35.9 wt% Ca).