occurrence, making it difficult to frame a definition that is
comprehensive and at the same time sufficiently precise for all cases. A
commonly used definition of a vein or lode is a mineralized mass of rock
which is followed for purposes of finding ore. The mineral matter may be
continuous or discontinuous. There may be one definite wall, or two
walls, or none at all. There may be associated gouges and altered or
mineralized rock. The vein may consist of almost any combination of the
elements of mineral matter, walls, gouges, and mineralized rock. Instead
of being a simple tabular sheet, a vein may have almost any conceivable
shape; it may consist of multiple strands of most complex relations; it
may have branches and cross-over connections. It may be a more or less
mineralized sedimentary formation with limits determined by original
deposition. It is very often bent or folded, and even more often
faulted; the faulting may be of great complexity, making it extremely
difficult to follow the vein. The vein may be cut by other veins of
different ages, which in places may be hard to distinguish one from
another. Erosion working down on a complex vein displaced by faulting
and folding may bring several parts of the same vein to the surface,
developing what seem to be separate vein apices. Where there are many
veins close together, it may be difficult to determine whether the
entire mass should be considered a unit vein or lode (a "broad lode"),
or whether each vein should be considered independently under the law.

The geologic aspects of these problems are obvious. There are few mining
districts where the vein conditions are so simple that no geological
problems are left to be solved with relation to extralateral rights. In
the early stages of the mining, separate operations may be carried on
for a considerable time in a district without mutual interference; but
as mining is carried down the dip, what seemed to be separate veins may
be found to be parts of the same vein or parts of a complex vein system,
and separate mining organizations are thus brought into conflict. It
then becomes necessary either to consolidate the ownerships or to go to
the courts to see which claim has the extralateral rights. In either
case, the geologist is called on to play a large part,--in the valuation
of rights for the purpose of combination, or in litigation to settle
apex rights. A geologic survey of the conditions is a prerequisite. In
ord