RERORD VON SLED DIRE Cl ORT O22 139 
solutions containing manganiferous carbonate and later by 
quartz, or on the other hand the carbonate band was a primary 
constituent of the original breccia and later replaced and cut by 
the quartz it is difficult to state positively. Anyway we have 
definite evidence in the banded and comb structures that the silica 
was introduced at a later time than the manganiferous carbonate. 
As we have seen, some residual products of the original Grenville, 
such as kaolin and vermiculite, have been found in some of the 
boxes which fact indicates clearly that a part of the original con- 
stituents of the vein must have consisted of fragments of Gren- 
ville marble and it is highly probable that the platy structures repre- 
sent the sheared off calcareous lining of the main fracture or even 
the fine-grained Grenville itself which was later replaced by 
manganiferous calcite and quartz. 
The dark bands or plates of manganiferous calcite have no 
developed crystals but occur as thin aggregations of carbonate 
grains which show perfect rhombohedral cleavage and —Y%4 R 
twinning. Having a hardness less than rhodochrosite but 
greater than calcite and responding quickly to the acid test this 
mineral is tentatively classed as a manganiferous calcite. 
These bands vary in thickness from one-fortieth to three- 
eighths of an inch, of variable length and have every possible 
angular relationship with each other. Though many bands are 
found cutting one another, it is believed that the mineral is all 
of the same generation. Dendritic markings of the dioxide, 
pyrolusite, are frequently found in the quartz plates to which the 
carbonate bands adhere. 
Interbanded with the manganiferous calcite in the banded 
structures, or lining the comb structures or the boxes of the 
cellular structures, is found a crystalline quartz with singly ter- 
minated pyramidons within the comb and cellular structures. 
The fringing character of the quartz on the carbonate plates, the 
intersecting of the carbonate plates and inclusions of the car- 
bonate in the quartz, all substantiate the conclusion that the 
quartz was of a later age than the carbonate. As a matter of fact 
these two minerals, the manganiferous calcite and quartz, may very 
well have formed so close together in point of time as to have been 
practically simultaneous. Otherwise there is difficulty in accounting 
for the formation of the box structure and its mineral contents. 
Many of the boxes are closed forms as must have been the 
original carbonate which filled the intersecting fractures which 
