: 
| 
’ 
of the Specular Iron-Ores of Santiago de Cuba. 429 
the individuality of some of which has been preserved within 
t mpass of their collective overflow. So considered, they 
eruptives, along with the altered alumino-magnesian silicates 
whose transformation has also been wholly or in part by loss 
of certain ingredients. 
abradorite-dioryte more or less chloritic and of metamorphic 
origin, as well as metamorphic representatives of a long series 
of intrusive species of rocks, have been described by Prof. Dana 
and the late Mr. Hawes. “The fact,” as remarked b ¥. 
Hawes, “that metamorphic action can produce rocks exactly 
like the igneous in external aspect and chemical constituents 
is of great interest in the study of rocks.”* It seems almost 
certain that ancient eruptives afford few if any standards for 
- Such comparison where permutations of the nature of metasoma- 
tism have not led to their resemblance to related metamorphics. 
This may be assumed especially in the case of chloritic and 
epidotic rocks. ; 
The chloritic products from alteration of the Sierra Maestra 
epidotic dioryte closely resemble, as above remarked, metamor- 
phic occurrences of chloritic schists. Such resemblances tend 
to indicate, indeed, a middle ground where meet products litho- 
logigally identical, proceeding on the one hand from basic erup- 
tive rocks by metasomatism, and on the other hand from sedi- 
mentary rocks by metamorphism. Resemblance between essen- 
tially chloritic aggregates of both types hardly needs the con- 
firmation of analyses. 
The dioryte of the Sierra Maestra, though not without traces 
of orthoclase, is essentially plagioclastic. The syenyte is mainly 
orthoclastic with occasional crystals of triclinic feldspars. The 
asalts indicated by Ansted in 1856 would now be classed as 
dioryte.+ 
* This Journal, 1876, xi, 126. + Proc. Geol. Soc., xii, 144, 
Lehigh University, Bethlehem, Pa., Oct. 10, 1884. 
