PART A: EXTRACTION INDUSTRIES IN GENERAL
1. The accumulation of raw materials usually entails some preparation, such as crushing to
render the material more uniform in size, or preliminary sorting to separate the useful portion from
the waste. If these operations take place in the extraction area, the buildings and equipment
employed are considered to be part of the extraction industry.
The following methods are used in extraction industries:
* Wood cutting
a. Mining, quarrying, oil and salt recovery, and dredging are typical of the extraction
b. Various mining methods are employed to extract a great variety of raw materials. Strip
mines are used when the ore or materials are in a thin layer near the surface. Open pit mines are
common where the material to be extracted lies close to the surface and in a massive body or thick
c. Quarries may resemble open pit mines, but the material extracted consists of rock or other
earthen material, rather than coal or ore. Bank or drift mines have a nearly horizontal tunnel into a
hillside; shaft mines enter the earth vertically or at a steep angle.
d. Dredges are used to collect sand and gravel, and to extract heavy minerals from placer
deposits, as well as to deepen rivers or channels for navigation.
e. The operations and equipment utilized in drilling wells for the recovery of gas, oil, salt and
sulfur all are similar. However, salt may be mined or recovered by evaporation in open ponds
called salt pans.