APPENDIX TO CHAPTER V. 
109 
APPENDIX TO THE TACONIC SYSTEM. 
The origin of the brown hematitic iron has been a subject of considerable inquiry; but 
very little light has been obtained upon the subject, until recently. Formerly my own 
opinion in regard to its origin, was, that it originated in a limestone shale, which was 
charged partly with oxide and partly with a decomposing sulphuret of iron. Such a mix¬ 
ture exists throughout the entire range of the formation, and is usually a bed subordinate 
to the Stockbridge limestone ; besides, the hematite occurs in beds connected with alluvial 
or diluvial formations, which appear to have been derived from decomposing or disinte¬ 
grating masses situated at some distance. I am inclined to maintain the opinion still, that 
such may have been the origin of many of the beds situated upon the ranges of this sys¬ 
tem. During an examination, however, of some of these beds near North-Adams in 
Berkshire county (Massachusetts), I found that the ore might be traced to veins which 
penetrated into the solid quartz rock or brown sandstone of the Taconic system. This vein 
is interesting, in consequence of being connected with a peculiar brecciated mass, which 
consists of sharp angular fragments of quartz cemented by the hematite. The fragments 
are often enveloped in a layer of hematite of a fibrous structure, or, in other words, in a 
fine variety of limonite. This investing coat is sometimes half an inch thick, and it 
frequently cements masses of fragments of great size and weight. The opinion which has 
usually prevailed in regard to this breccia, is that the rock was broken thus by some cause 
unknown, and the fragments subsequently cemented together by infiltration of the oxide 
of iron. This mode of formation is not very objectionable, inasmuch as we frequently see 
operations of a similar kind now in progress. But we may very profitably inquire whether 
it is applicable to all cases; and whether, if we even admit it as true in part, we may not, 
under certain circumstances, adopt a different view of its origin ? The first inquiry is, how 
came the quartz in this form, broken and even apparently comminuted, and the fragments 
as sharp and splintery as though they were just broken with a hammer'? Pursuing our in¬ 
quiries, may we not ask ourselves whether there is any connection between the force which 
broke the quartz as described, and that which effected the cementation subsequently ? As 
to the Adams vein, in connection with the brecciated mass, the enquiry, taken in connec¬ 
tion with the origin of veins, seemed very natural. Thus, adopting the view that veins 
are rents filled with molten or ignited matter, it appears highly probable that the oxide 
of iron or hematite might have been forced up from below ; and, when it reached the 
surface, it may have flowed into the natural joints of the quartz rock, and have farther 
broken the bed by the sudden application of heat, and hence consolidated the fragments 
as we now find them. All the known facts which are at all concerned in the inquiry, go 
to show the probability of this view of the subject. Thus, heat applied suddenly to this 
vitreous quartz would have the effect we have supposed, namely, to fracture it : the filling 
