144 TRANSACTIONS OF THE [aPR. 21, 



We have datolite, heulauclite, stilbite, chabazite, and analcite, 

 — in each case deposited on the surface of the quartz, and 

 quartz crystals deposited upon pseudomorphous quartz, showing 

 that they have all been secondary deposits. 



The cuprite is often in minute crystals and radiating rosettes; 

 the chalcopyrite is also in small crystalline masses. 



The chalcedony pseudomorphs after pectolite in some cases 

 form beautiful tabular plates; in other places the radiations of 

 the pseudomorphous chalcedony may be followed through the 

 changes to the concentric markings of fortification agate, with 

 no resemblance to pectolite. We find some of the cavities lined 

 with a thick, chalky cream, soft when first opened, but becom- 

 ing hard upon exposure. It has the nodular appearance of 

 hyalite or chalcedony, but milky-white in color and not trans- 

 lucent. This I have labelled nascent chalcedony. In other 

 cases we find the process seemingly farther advanced, stage by 

 stage, to the semi-transparent chalcedony, often in beautiful 

 microscopic nodular or stalactitic shapes. 



This quarry is interesting, not only to me, the unscientific 

 collector of the beautiful and curious in nature, but also to those 

 who are true scientists, engaged in investigating the secrets of 

 nature's works. 



It seems to me that here we have exhibited the workings of a 

 chemical and physical laboratory on a grand scale. Not only the 

 effect of the great heat of nature's furnace, when this basalt was 

 thrust through the crust, as shown by the baked red sandstone 

 on the exposed surface which was in contact with it, but by the 

 vesicular, lava-like amygdaloid, and by the larger cavities in the 

 basalt lined with crystals of zeolites and other minerals. 



We have also shown the results of more direct chemical action, 

 beginning with the decomposing effect of the atmosphere and 

 water, which probably first attacked the sulphides of copper ; 

 then having the aid of sulphurous acid, in addition to the car- 

 bonic acid with which it was already charged; the alkalies, lime, 

 and sodium from the decomposition of calcite and pectolite; and 

 other chemical agencies which suggest themselves. 



It is but fair to say that no chemical analysis of these minerals 

 has been made. I have named them entirely upon my own re- 

 sponsibility, guided by their general appearances and some of 

 their physical properties. 



President Newberry made some very interesting statements 

 in regard to the formation of cavities in the soft rock by gases, and 

 the subsequent deposit of minerals in these cavities by hot solu- 

 tions. 



