36o 
The America?! Geologist. 
Docomber, 1899 
Calcu/afed loss of material in f lie fresh and decomposed >ock. 
Fresh Decoin- Calculated amounts saved 
posed and lost 
Constituents I II III IV V 
Percent- Percent- Percent . 
BuJk Hulk asro loss ase of age of 
analysis analysis for entire each cou- eacli con- 
rock stituent stitiient 
saved lost 
Si02 51.08 42.07 21.66 57-59 42.41 
AI2O3 23.58 32.05 1. 17 95.04 4.96 
*Fe203 6.85 9.83 00.00 100.00 00.00 
CaO 9.36 0.95 8.69 7.10 92.90 
MgO 4-95 1.38 3.98 19.51 80.49 
MnO 0.39 0.48 0.04 87.27 12.73 
^h.. ............ ..'. \ ^-^4 I -11 1-56 33-23 66.77 
Igni 12.13 00.00 fioo.oo 00.00 
Total 100.00 100.00 37.10 Vo 
Columns I\' and V show the percentages saved and lost, 
respectively, for each constituent calculated on an iron con- 
stant basis. Of the individual constituents, 42.41 per cent of 
th'e SiO^ 4.96 per cent of the AUOa, 92.90 per cent of the CaO, 
80.49 P^r cent of the MgO, 12.73 per cent of the MnO, and 
66.77 per cent of the alkahs (Na^O+KsO) have disappeared, 
equivalent to a total loss for the entire rock of 37.10 per cent. 
Out of the 2i7 • 10 per cent, total percentage loss for the en- 
tire rock, approximately two-thirds of the whole, or 21.66 per 
cent, is SiO^; 8.69 per cent, or a fraction more than one-fourth 
of the whole, is CaO; a little more than one-tenth, or 3.98 per 
cent, is MgO ; while the Al^Os and K^O+Na-O combined only 
amount to about one-fiifteenth of the whole. It is at once no- 
ticeable from the table that the greatest total loss for the rock 
is in the three constituents SiO.^iCaO and MgO, the sum total 
of the three removed by solution, amounting to 34.33 per 
cent; the remaining 2.77 per cent of the 37.10 being divided 
between the Al-O-, alkalis and MnO. Attention is here called 
to the slight loss in the AkOs, which is accounted for later on 
in the discussion. The relative loss in the remaining constitu- 
*Iron was determined as total F2O3. 
tGain. 
