Cross and Hillebrand—M'narah from Colorado. 129 



It is only by the adoption of names based upon purely mine- 

 ralogical differences that we can hope to ob1 

 that shall conform to the three fundamental principles of Uni- 

 formity, Stability, and Adaptability. 



As it is not to be hoped that a sweeping reform in petro- 

 graphical nomenclature can be carried out at once, the good of 

 the science requires that at least the first and most important of 

 these principles, viz: Uniformity, should be recognized and i 



conformity therewith that all shoi 



ild use j 



some on 



e published 



and easily accessible system of nam 



<,s until ;i 





>mplete sys- 



tern of names can be offered with 



somech; 



mce tin 





generally adopted. 









In the opinion of the writer, the 1 

 as recorded in his " Massige Gesteir 



lomenclature of Eosenbusch 



ie, 1877,' 



is the i 



nost widely 



recognized and the best now access 



ible. 







University of Cat., Berkeley. 









Art. XVI.-' m„* < >> , ,n /'- U X <. \>, , II , , 

 Mountain D * v n I <Jn th )// d <■,'/'» , ,, 

 ring in the basalt of liable Mountain, near Golden, Colorado; 

 by Whitman Cross and W. F. Hillebrand. 



(Continued from page 458, vol. xxiii.) 

 4. Apophyllite. 



This mineral occurs in well-developed crystals of prismatic 

 habitus, with *-j (oo Poo) and 1(P) predominating, while 0(0P) 

 is in most cases quite subordinate, or wanting entirely. The 

 larger crystals, which are occasionally half an inch in diameter, 

 are often" of a greenish tinge, sometimes quite pronounced, and 

 possess more or less uneven surfaces produced by a repetition 

 of the crystal faces, so that the termination is made up of a 

 large number of small pyramids. 



The prismatic surfaces are roughened by depressions or ele- 

 vations, bounded by prism and pyramid planes. This feature 

 is very prominent in all large crystals. The smaller ones are 

 in contrast sharp and clear, with smooth, brilliant faces. Espe- 

 cially noticeable on these small and clear crystals, though not 

 peculiar to them, is a replacement of the pole edge of the pyr- 

 amid, by a small reentering angle formed by pyramid faces. 

 This angle is nowhere prominent, yet may be easily identified 

 on all clear crystals both large and small. No corresponding 

 irregularity of any kind could be detected on the dimetric 

 prism of these crystals. 



As a rule, the largest crystals occur in the small cavities, 

 and their growth has been more or less hemmed by the walls, 



Am. Jour. Sci.— Thirl m un>, Vol. XXIV, No. 140.— August, 1882. 



