X-R-ay Analysis of the Gingin Upper Greensand. 
237 
of hydration. The data relating to glauconite was taken from Gruner (12), 
who, by refemng the mineral to the mica structure, was able to assign Miller 
indices to most of Ids recorded lines. 
Quartx data was taken from Favejee (16) who has tabulated estimated 
interplanar spacings relating to the unit cell a = 4-903 A, c - 5*393 A. Data 
supplied by Ifanawalt, Riim and t revel (17) was used when considering the 
possibility of the presence of the oxides and hydroxides of Fc and Al. 
In preparing Table I. the ])rinciple was eiujiloyed of only assigning an 
origin to a lino \vhen on intensity considerations the line was likely to bo 
contributed to by the mineral in (juestion. 
Consideral>lo difficulty was encountered in recording 10 A diffraction lines 
because a pronounced central scattering extended out to about this spacing. 
Measurements of spacings in this region consequently vary considerably. 
Films taken with Cu radiation, however, often gave clear evidence of the 
existence of a 10 A line. 
(1) Upper Greensand, 
1 he original observations of early workers on the high glauconite (’ontent 
of this sand have been confirmed. A comparison between the fine and coarse 
fractions seems to indicate that there is a higher glauconite content in the 
coarse fraction. I'he agreement between the glauconite spacings listed by 
Gruner and the spacings recorded for the coarse fraction of tlio uiijier groi'nsaiul 
is sufficiently good to i:»ermit of a calculation of the unit cell dimensions of the 
Gingin glauconite assuming the mica structure of glauconite and the indices 
assigned by Gruner to the various spacings. In this calculation the following 
lines and corresponding indices were used : 10-12 A (002) ; 2-o8 A (2o¥) • 
1*510 A (000) ; 1*305 A (400). 
Table 11. 
IXIT CELL 1)IMEN8I()NS 
OF GLAITOMTE. 
Gingin glauconite. 
Gruner’s average of 
six sam])les. 
('o 
20-21 
1 
o 
ba 
9 -00 
9-07 
^0 
5-24 
5-24 

94° 58^ 
95° m' 
Simpson (18) has noted the presence of dufrenite (a bright green basic 
ferric phosphate Fe 2 ( 0 Pr) 3 P 04 ) in the upper greensand but in the absen(‘e of 
any X-ray data, known to the author, with resp(a*t to this miruu-al and in fhe 
absence also of reasonably pure specimens fVoni which X-ray data may be 
obtained, no conclusion has been reached as regards its presence in the sample 
examined in this study. The jirestnice of (|uartz: lias beta) prex'iouslv 
refernHl to. 
(2) Subsoil. 
The most noticeabk' differences between this pattern and tlu' jirevious one 
ai(> the existence of a 15 A and a 7 A spacing. The 15 A spacing shrinks to 
10 A and the 7 A spacing disappears when the sample is licated to 500°C. 
