WATSON AND GOOCHI VIVIANITE FROM FLORIDA 87 



The composition of the matrix is shown in the analysis given 

 in table 2, The sample analyzed was representative of the ma- 

 trix, except that care was taken in selecting the sample to avoid 

 as far as possible the inclusion of phosphate pebbles. 



TABLE 2 

 Chemical Analysis of Vivianite Matrix (By S. D. Gooch) • 



Si02 4.17 



AUO, 4.96 



FesO, 65.20 



FeO 1.41 



MgO trace 



CaO 1 . 68 



N^\ 0.16 



H2O - 10o°C 4.14 



H2O + 105°C 12.72 



MnO . 56 



TiO. 0.14 



PoOo 5 .02 



F trace 



SOa none 



C02 none 



100.16 



The analysis clearly indicates that the matrix is not a clay, 

 but an earth composed of the hydrates of iron and aluminum, 

 chiefly the former, hydrous phosphates of calcium, iron, and 

 aluminum, and some free quartz. It is characterized by the 

 essential absence of hydrous silicate minerals, especially kaolinite, 

 a fact confirmed by microscopic study. The slight insoluble 

 residue left on boiling a portion of the matrix in dilute hydro- 

 chloric acid was found to be composed of quartz and not of 

 silicate minerals. 



RELATIONS OF VIVIANITE TO THE ASSOCIATED MINERALS 



The principal associated minerals are hydrous oxide of iron, 

 probably limonite chiefly, calcium phosphate forming the phos- 

 phate pebbles, and rounded grains of quartz. The relations of 

 the vivianite to these minerals clearly indicate its later forma- 

 tion, for the vivianite frequentl}^ incloses phosphate pebbles and 



