GEOLOGICAL SURVEY OF THE TERRITORIES. 



l'B3 



Orifice 2s"o. 2 is 3 feet above tlie first. It is 1 foot in diameter and 12 

 feet deep. Besides these principal openings there is a large number of 

 smaller orifices and springs scattered over the platform, some of which 

 are quiet and some of which spout. Some of the temperatures are as 

 follows : 194° F., ISSo F., 182° F., 198o F., 19Go F., 194° F., I860 F., 

 19GO F., 1940 F. ; air, (38° F. ; time, 4.25 p. m. The water in the Giant 

 seemed to be considerably agitated, but never reached a greater height 

 than about 3 feet above the top of the cone. The platform is made up 

 of successive layers of geyserite, and on the side next the river the 

 water has so cut into it that the layers are well exposed. They are 

 very irregular in composition, but as a rule the lower we go the harder 

 we find tbem. In one of the layers I obtained pieces that bore a 

 remarkable resemblance to true opal, the color and specific gravity being 

 that of semi-opal rather than geyserite. The colors are white, red, and 

 green. Two of these specimens were submitted to Dr. F, Endlich, of the 

 Smithsonian Institution, who has sent me the following communication 

 in regard to them. 



Washington, D. C. 

 Deae Sir : I have examined the specimens from the Giant Geyser that you Lave 

 kindly submitted to me, and give you herewitli the results. From their position at 

 the crater of the geyser, it maj' be deduced that they are older than the geyserite at 

 the surface. The minerals form plates of about -J to 1 inch in thickness, lying horizon- 

 tal when in position, and are also distributed in irregular nodules, bordered on all 

 sides by geyserite. For particulars in regard to locality I refer to your report. The 

 varieties obtained are two, as follows : 



No. 1. — Structure, amorphous ; hardness, 6-6.5 ; siiecific gravity, 2.4903 ; color, 

 milky white ; fracture, sub-conchoidal ; luster, dull. 



Analysis. 



Per cent. 



Loss by ignition 1. 50 



Silica .' 95. 84 



Ferric oxide 2. 68 



Soda* Trace. 



Litbiam* Trace. 



Calcium* Trace. 



Alumina Trace. 



Total : ' 100.02 



Xo. 2. — Structure, amorphous ; hardness, 6-6.5 ; specific gravity, 2.0816 ; color, light- 

 greenish brown ; fracture, conchoidal ; luster, vitreous. Water, 6.3 per cent. 



Comparing with quartz, opal, and geyserite, we find the position of this mineral iis 

 follows : 





Hardness. 



Specific gravity. 



Percentage of 

 silica. 



Percentage of 

 water. 



Quartz 



. 7 



6. 0-6. 5 



6. 0-6. 5 



5-5-6.5 



5.0 



2. 5-2. 8 



2.4 



2.08 



1. 9-2. 3 



1. 8-2. 



99 

 95 



3 



Specimen No. 1 



Specimen No. 2 



1.5 

 6.3 



Opal 



93 



87 



7.00 



Geyserite 



10 00 







We therefore have a mineral resembling in some points semi-opal ; in this case, 

 however, having but little water, a comparatively high specific gravity, and an entirely 

 new process of formation for any mineral, occupying, as it does, an intermediate posi- 

 tion between quartz and opal. As the characteristic feature of opal is the presence of 



* By spectroscopic examination. 



