228 GEOLOGY AND GOLD DEPOSITS OF THE CRIPPLE CREEK DISTRICT. 
The volcanic rocks of Cripple Creek are rich in combined water. The average 
of the analyses shows 1.62 per cent combined water given off above + 110° C., and 
they range from 0.69 to 2.09 per cent. To a large extent this is contained in 
analcite, the primary nature of which is proved. Some of the phonolites contain 15 
per cent of this analcite and the latite-phonolites average 4.6 per cent. To a smaller 
extent the water is present in kaolin or other secondary hydrous minerals. It is 
assuredly not an exaggeration to say that the rocks contain an average of 1 per cent 
of combined primary water. The presence of primary water being firmly estab¬ 
lished, it follows, if the statement in the preceding paragraph is true, that the magma 
contained much more of it at greater depths. The water lost as steam by the intru¬ 
sive bodies under our present range of observation doubtless partly permeated the 
rocks and was partly dissipated in the air at the time of the eruption. But unques¬ 
tionably there are large intrusive masses which did not attain the level of those 
now visible, though they rose to much higher levels than they originally occupied. 
Their water was probably partly expelled from the cooling mass, but was held in its 
confines under strong pressure, having abundant opportunity to dissolve the other 
substances which may have emanated from the magma. As the volcanic mountain 
settled down deep fissures were created, which reached to the levels of these stored 
hot waters and afforded them means of escaping toward the surface. Such is the 
explanation of ore deposition by “magmatic” or “juvenile” waters, to follow 
Suess’s terminology, and to these we are inclined to attribute the largest share of 
ore deposition, possibly the whole. The storage reservoir was limited, and the 
supply of these strange solutions was soon exhausted. Surface waters followed 
the retreating juvenile waters and filled the “sponge in the cup” until equilibrium 
was established. At the present time the volcano appears extinct, and yet a few 
hundred or a thousand feet below the surface the faint exhalation of carbon 
dioxide and nitrogen are met—the last volatile products of the phonolitic magmas. 
MODE OF DEPOSITION. 
The laws governing the actual deposition of materials in mineral veins are little 
known, and it must be confessed with regret that the last ten years have not seen 
much direct advancement, although the foundations for it have been laid broad 
and deep by the development of physical chemistry. We have reached a point 
where further progress depends on experimental work with solutions at high tem¬ 
perature and pressure. , , 
If an alkaline solution, such as is indicated above (p. 224), with an unascertained 
state of ionization, ascends in fissures through porous volcanic rocks, a most com¬ 
plicated set of reactions will follow. Pressure and temperature will constantly 
change, certain compounds will be precipitated, and constant changes in the com¬ 
position of the solution will take place. It is further to be considered that the 
solutes 0 or some of them may diffuse through the walls and that different ions may 
diffuse at various rates. It is even possible that the walls in places maj" act as 
semipermeable membranes which will allow not any solutes to pass. There is also 
the chemical action of the solutions on the porous rocks, with attendant loss of 
a Solute in physical chemistry means the substance dissolved; solvent indicates the medium in which the substance is 
dissolved. 
