k;xi:< >rs poemation. -Jd'S 



one cavity, and with a general order of succession, to which, however, 

 many exceptions may In- noticed. 



The species stilbite, laumontite, thomsonite, and calcite have another 



form of occurrence, in reddish or yellowish deposits whose characteristics 

 will lie specially discussed. The color of the minerals in these cases is due 

 to ferric oxide in chemical combination in the silicates, and the deposits 

 thus marked are older than the white or colorless varieties of the same 

 species. 



In regard to the occurrence of the white or colorless zeolitic species, 

 nothing has been observed which appears to characterize this locality. 

 They are found in greater or less abundance throughout the basaltic masses 

 of both parts of Table Mountain in all kinds of cavities, but an- besl 

 developed in the broad amygdaloidal zone of North Table .Mountain. On 

 all sides of the mountain the naturally exposed vesicles are found to contain 

 zeolites in well-developed crystals, but on account of the blasting which 

 has been done on the southern face of the mountain, near Golden, most 

 of the described material has been obtained at this place, the crystals being 

 fresher and cleaner than on weathered surfaces. 



Nearly all of these species have a wide range throughout the mountain 

 and also in the cavities of different portions of the basaltic masses. Scolecite 

 and levynite have been clearly identified only at the main locality above 

 referred to, ami there only in the upper part of the amygdaloidal zone, 

 in small pores, and usually with but t\-w associates. Natrolite is also 

 comparatively restricted in its occurrence, and appears to be most common 

 on South 'Fable Mountain. 



For details concerning the development of individual species the reader 

 must be referred to the publications cited above. Analcite, apophyllite, 

 chabazite, stilbite, thomsonite, and calcite are found varying greatly in 

 perfection and size. All but thomsonite occur in well-formed crystals in 

 many places. Thomsonite is found only in radiate aggregates or spherules 

 forming mannnillary crusts. Scolecite is developed after the same manner 

 as thomsonite, while natrolite occurs in long, acicular crystals more or less 

 isolated. Levynite appears in crusts of small tablets set on edge. Mesolite 

 is developed in minute spicules which form sponge-like masses or are woven 

 into delicate films. 



