98 



MARINE BOTTOM SAMPLES OF LAST CRUISE OF CARNEGIE 



Table 32. Intensities of quartz lines for different size fractions of northeast Pacific red clays 



Symbols refer to intensity of characteristic spacings for substances indicated: vs = 

 characteristic spacings are very strong in pattern; ws = very, very strong; s = strong; 

 ms = moderately strong; mw = moderately weak; w = weak; ww = very, very weak; tr = 

 trace; ? = spacings are possibly present or some spacings are missing. 



chloride in many of the Globigerina oozes is owing to 

 imperfect washing of the samples. Owing to the high 

 symmetry of this substance, very small amounts of it 

 give disproportionately strong diffraction lines. The 

 lines of calcite are dominant in every sample, whereas 

 only very small amounts of aragonite were detected in a 

 few of the samples. Phillipsite was found definitely in 

 only three of the analyzed calcareous s?mples--nos. 16, 

 22, and 27--and possibly also in no. 25. Quartz was 

 present in samples 14, 17, 19, 22, 23, 25, 27, 43, 53, and 

 81. The presence of the typical clay line at 4.45 ang- 

 stroms indicated the existence of a clay mineral in all 

 samples except the silt grade of sample 17 and the part 

 less than 1.0 micron in size of sample 21. In general, 

 the patterns given by the true colloidal materials ob- 

 tained from samples 17, 19, 21, 23, and 81 exhibit fewer 

 lines than those given by coarser separates such as 

 those from samples 16, 22, and 27, which indicates a 

 simpler constitution of the former. A few lines in sam- 

 ples 22 and others could not be identified. 



Samples of Low CaC03 Content 



Figure 37 shows the patterns of interplanar spacings 

 obtained from certain red clays, nos. 70, 72, 73, 74, and 

 77, compared with those of quartz, muscovite, kaolinite, 

 and montmorillonite, and of soil colloids 431 and 7083 

 given by Kelley, Dore, and Brown. 



The increasing complexity of structure and compo- 

 sition with increasing particle size is well shown in the 

 noncalcareous samples, the analyses for coarser size 

 grades showing in every case many more lines than 

 those of colloidal particle size. The presence of many 

 well-defined lines even in the finest-grained samples 

 shows conclusively that at least a considerable part of 

 these materials are definitely crystalline and not 

 "amorphous" as was thought to be the case by Murray. 



Examination of table 29 and of the graph shows con- 

 clusively that quartz is present in every noncalcareous 

 sample examined, the three most prominent quartz 

 lines at 3.33, 1.81, and 1.37 angstroms being present in 

 every sample. It may be seen that the amount of quartz 

 decreases directly with the particle size, a conclusion 

 which is confirmed by a comparison of chemical analy- 

 ses of certain whole samples with analyses of the colloi- 

 dal fractions of the same samples. This is illustrated in 

 table 32 which shows the intensity of the three principal 



quartz lines (3.33, 1.81, and 1.37 angstroms) given by 

 the coarse and fine fractions of samples 70 to 77, inclu- 

 sive, together with the silica sesquioxide ratios of the 

 entire samples and of the colloidal fractions. It will be 

 noticed that this ratio varies from approximately 4 in 

 the entire samples to about 2.5 in the colloidal fractions; 

 correspondingly, the quartz lines vary from strong to 

 weak with decreasing particle size. 



Nagelschmidt concluded (from a comparison of 

 his X-ray examination of marine Middle Oligocene clay 

 from Maliss in Mecklenburg with the chemical and 

 optical investigations of Schlflnz [1933] on the same ma- 

 terial) that quartz, in comparison with the other miner- 

 als which occur in clay, is easily detected because of 

 the relatively strong reflecting power of its crystal lat- 

 tice. Powdered quartz less than 0.6 micron in diameter 

 showed no widening of the lines or decrease in intensity. 

 On the other hand, the powder diagram of the fraction 

 less than 0.05 micron in particle diameter of the Maliss 

 clay contained no quartz lines, even though chemical 

 analyses showed 15 per cent free silica. Nagelschmidt 

 suggests that the silica in this fraction may be" amor- 

 phous. 



Owing to imperfect washing, small quantities of so- 

 dium chloride are present in samples 10, 30, 35, 49, 51, 

 56, 60, 62, 70, 79, the fraction less than 30 microns in 

 particle size of sample 73, and the fraction less than 4.5 

 microns in particle size of sample 77. Calcite is found 

 in samples 10, 30, 51, 56, and 62. Phillipsite is definite- 

 ly present in small quantity in the fraction less than 4.5 

 microns in particle size of sample 77, and is probably 

 present in samples 30, 49, 60, 62, 70, and the fraction 

 less than 30 microns in size of sample 73, but the appar- 

 ent absence of the strong phillipsite line at 2.70 ang- 

 stroms makes its determination in these samples uncer- 

 tain. It should be pointed out, however, that with the 

 apparatus used, the detection of the presence of weak 

 lines occurring near strong ones is difficult, especially 

 in patterns of materials which give diffused lines and 

 more or less generally darkened films. 



The fine fractions less than 1 micron in particle di- 

 ameter of samples 31, 34, 69, 70, 72, 73, 74, and 77 have 

 patterns agreeing very closely, both in intensity and nu- 

 merical values of the spacings, with the patterns given 

 by Kelley, Dore, and Brown for colloids from two Cali- 

 fornia soils, nos. 431 and 7083. Optical studies by Pro- 

 fessor A.O.Woodford of the clay mineral in soil 431 gave 

 the following indlces.a =1.554, /3 =1.569,7 =1.569, and for 



