GEOLOGY OF THE NORTHERN ADIRONDACK REGION 



351 



1 Diabase from summit of Mt Marcy, Essex co. Analyst Leeds. N. Y. 



State Mus. 30th An. Rep't, p.102. 



2 Diabase from shore of Upper Chateaugay lake, Clinton co. Analyst Eakle. 



Am. Geol. July 1893, p.35. 



3 Diabase from Palmer hill, Black Brook township, Clinton co. Analyst 



Kemp. U. S. Geol. Sur. Bui. 107, p.26. 



4 Olivin diabase, Bellmont township, Franklin co., dike 13. Analyst Morley. 



18th An. Rep't N. Y. State Geol. p. 120, and 20th An. Rep't, p.r79. Very 

 fresh, olivin not perceptibly serpentinized. 



5 Olivin diabase from shore of Upper Chateaugay lake, Clinton co. Analyst 



Eakle. Op. cit. p.35. 

 G Very basic syenite porphyry, Rand hill, Clinton co. Analyst Morley. Geol. 

 Soc. Am. Bui. 9 :248. 



7 Normal syenite porphyry, Rand hill, Clinton co. Analyst Morley. Op. 



cit. p.248, and 20th Am Rep't N. Y. State Geol. p.r79. 



8 Syenite porphyry from shore of Upper Chateaugay lake. Analyst Eakle. 



Op. cit. p.34. 



9 Acid syenite porphyry, Rand hill, Clinton co. Analyst Morley. Op. cit. 



p.248 and r79. 



The analyses quoted above are all that are known to the writer 

 of these rocks. Many of them are quite old but are valuable for 

 comparative purposes, though not going into the minutiae of 

 modern requirements. The diabases show considerable variation, 

 as would be expected, yet on the whole harmonize well with one 

 another. No. 4 is the only tolerably complete analysis, and at 

 the same time seems to represent about a mean between the 

 extreme types and will hence serve as a fair representative of the 

 average diabase of the district. It consists essentially of labra- 

 dorite and augite in about equal amounts, with considerable 

 olivin and magnetite and a rather unusual amount of biotite, 

 much of which is clearly primary. Apatite is about the only other 

 mineral. The magnetite is onl}* slightly titaniferous, if at all, 

 since the very small amount of titanium present may likely all 

 be in the biotite. The augite is in two generations, but the 

 feldspar not. The structure is only poorly ophitic. 



No. 1 is the rock long ago analyzed by Leeds, the analysis not 

 being accompanied by any description however. Augite is the 

 only mineral specifically stated to be present. 



No. 2, according to Eakle, appears to lack olivin, and the augite 

 is almost wholly altered to chlorite and epidote. No. 5, accord- 

 ing to the same author, is an ordinary olivin diabase, though he 

 makes no mention of augite, and it is only inferentially supposed 

 to be present. It is noteworthy in being exceptionally acid for 



