GEOLOGICAL SURVEY OF THE TERRITORIES. 



153 



Orifice 'No. 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 Vvhich spout. Some of the temperatures are as 

 follows : 1940 j?., 188° F., 182° F., 198° F., 19Go F., 1940 F., 180° F., 

 19GO F., 1910 F. ; air, 08° 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 them. In one of the layei'S 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. Eiidlich, of the 

 Smithsonian Institution, who has sent me the following communication 

 in regard to them. 



Washington, D. C. 

 Dear Sir : I have cxamiued tlie specimens from the Giant Geyser that you have 

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

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

 the siu'face. The minerals form plates of about 4^ to 1 inch in thickness, lying horizon- 

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

 sides by geyserite. For particulars in regard to locality I refer to j'our report. The 

 varieties obtained are two, as follows : 



No. 1. — Structure, amorphous ; hardness, 6-6.5 ; specific 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. 



Lithium * Trace. 



Calcium* Trace. 



Alumina Trace. 



Total 100.02 



No. 2. — S(:ructure, amorphous ; hardness, 6-6.5 ; specific gravity, 2.0816 ; color, light- 

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



Compariug with quartz, opal, and geyserite, Ave find the position of this mineral as 

 follows : 



Quartz 



Specimen No. 1 

 Specimen No. 2 



Opal 



Geyserite 



Hardness. 



7 

 6. 0-6. 5 

 6, 0-6. 5 

 5.5-().5 



5.0 



Specific gravity. 



2. 5-2. 8 

 2.4 



2.08 

 1. 9-2. 3 

 1. 8-2. 



Percentage of 

 silica. 



99 



95 



93 



87 



Percentage of 

 water. 



0.3 

 1.5 

 6.3 

 7.00 

 10.00 



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

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

 now process of ibrniatiou for any mineral, occupying, as it does, au intermediate posi- 

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



By spectroscopic examination. 



