THE SCOPE OF ECONOMIC GEOLOGY 7 
present in the district traces of them should be found, such 
as grains of tin ore, which would probably be associated with 
fragments of black tourmaline (schorl) and topaz. If the 
miner has failed to find in the alluvial beds any gold, 
platinum, tin, or gems, he would turn to the hills or areas 
of exposed rock in the hope of finding other minerals. He 
would search for quartz or calcite, and in them for metallic 
minerals, which in most veins would originally have been 
sulphides. In a moist climate the sulphides near the sur- 
face are oxidized and removed in solution. Some of the 
iron would probably have been deposited as iron oxide, 
staining the vein brown or red. Sulphides of copper would 
have been dissolved, and possibly redeposited as the green 
carbonate, malachite, or as plates or strings of native copper. 
If the vein contained lead the top of the lode would probably 
contain cerussite, the carbonate of lead. 
Iron-bearing lodes and seams of coal and oil shale would 
be noted as resources available for the future. Lodes con- 
taining the precious metals or the more valuable of the base 
metals, copper, lead, zine, nickel, etc., would be prospected 
to determine their grade or proportion of valuable constituents. 
STRUCTURE OF Loprs—The simplest form of lode is a 
metalliferous vein traversing the bedrock, 
which is technically known as the country, 
Veins are sheet-like in form and range from 
horizontal to vertical. Each lode or vein 
is bounded by two walls or cheeks, of which 
the upper is known as the hanging-wall, and 
the under as the foot-wall. The horizontal 
direction of a vein is its strike or course, 
The inclination from the horizontal is the 
dip (Fig. 1) ; the inclination from the verti. Fie. 1.— Diagram 
cal is usually the more useful measure- oF 4 Lope. 
ment, and is the underlay or hade. A AB, strikes, Bo, 
lode may consist of a single vein or may be i Aug ’ ’ 
compound. A compound lode consists of a 
series of veins, either of the same or different materials; the 
veins may be parallel, or divergent, or in a network, or may 
be mixed with masses of broken country. The simplest lodes 
are those deposited in fissures, which are of two chief kinds. 
The first are clefts of which the walls have been pulled apart