

246 STRUCTURAL AND FIELD GEOLOGY — 
or other veinstone; to this may succeed two bands of ore, 
one on either side—and such duplication may be repeated 
again and again, until the fissure is completely filled (Fig. 98). 
Such a banded lode is said to 
be symmetrical, The crystal- 
lised minerals are often pris- 
matic—their longer axes being 
perpendicular to the walls and 
their pyramidal terminations 
directed towards the centre of 
the vein, A sections yaeness 
such a sheet has suggested to 
mining folk its resemblance to 
a comb, and thus we have the 
FIG. 98.—LAMELLATED LODE: WITH iy oe es ie PP jedi 
DeueEe. F symmetrical fissure-veins, Fre- 
quently, the fissures are not 
cempletely filled—medial cavities of less or greater extent 
being left. These are termed vughs or druses, and are 
usually lined with crystallised minerals. 
(c) BRECCIATED STRUCTURE.—Some lodes are largely 
brecciated—abundant fragments of mineral plates or lamelle, 
together with pieces of the country-rock, being scattered 
through amorphous or ir- 
regularly crystallised vein- 
stuff. This structure shows 
that the fissure occupied by 
a banded lode has been 
subsequently reopened — 
the crustal movement re- 
sulting in the fracturing 
and shattering of the platy 
layers of the original lode 
and the introduction into 
the reopened ffissure of 
fragments of the country- FIG. 99.—BRECCIATED LODE. 
rock. Later on, this 
jumbled mass has been permeated by metalliferous and 
mineral solutions, which have bound the débris together (see 
Fig. 99 and Plate L. 2). Now and again these subsequently 




