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Struvite rather than apatite or amorphous calcium phosphate is precipitated when phosphate is added to seawater containing more than 0.01M NH4+ ions. Struvite may have precipitated from evaporating seawater on the primitive earth, and may have been important for prebiotic phosphorylation.
Orthopyroxene of various compositions are reported in the less than 1 mm fines in lunar soil sample 14163. The mineral occurs as individual grains and as a major and minor constituent in lithic fragments. K is not positively correlated with REE and P in the orthopyroxene-containing igneous rock fragments studied. Although an X-ray powder pattern of the rare earth element containing calcium phosphate is that of whitlockite, it is tentatively concluded that the weak pattern observed results from an intimate admixture of a major amount of an amorphous phosphate of unknown composition with a lesser amount of crystalline whitlockite.