Question

Question 1)
About 90% of the gold ever mined throughout human history is still in circulation; however, only about 55% of all the silver ever mined is still in circulation.  Why do you think there is such a difference?  Explain. 

Question 2)
Categorize each of the following words or phrases as being associated with either open-pit mining (O) or underground mining methods (U)
dust and sedimentation problems                 ["U", "O"]      
  use drifts and stopes                                   ["U", "O"]         
 more dangerous                                              ["O", "U"]         
 best for disseminated ores                             ["O", "U"]         
 more waste  
 ["U", "O"]   
 use benches 
   ["O", "U"]         
 best for vein ores                           
 ["O", "U"]           
far cheaper
  ["O", "U"]           
requires high grades
     ["O", "U"]

Answer 1

Ans-1) About 90% of the gold ever mined throughout human history is still in circulation; however, only about 55% of all the silver ever mined is still in circulation.Their is such a difference because- Silver is is the best element to conduct heat and electricity and due to this reason it has been widely used by electronic and medical industries.Beside its excellent properties it is much cheaper than gold (about 100 times).

Silver now a days widely used in antimicrobial agent in medical applications, solar panel,mobile batteries,electronics chips,different types of screen,mobiles,pc,etc.

And the main reason for such less percent of circulation of silver is that it cannot be recycled economically from the above mentioned products,and hence it end up in landfills and dump areas.

Ans-2) open-pit mining method is represented as (O) and underground mining method is represented as (U).

1) Dust and sedimentation problems-Ans is (O),because in the open pit mining they are directly exposed to the environment causing such type of problems.

2) use drifts and stopes-Ans is (U),because stope is defined as the open space left after the removal of minerals from the underground mine whereas drifts is defined as underground mine in which the entry is above water level and generally on the slope of a hill.

3) more dangerous- Ans is (U),because it can cause severe respiratory problems to the workers due to dust particles and poisonous gases, also risk of collapsing is higher in this case.

4) best for disseminated ores-Ans is (U) because it is found deep inside the earth surface and Access to deeply buried ore bodies is attained through underground mining.

5) more waste- Ans is (O) because it produce lots of waste rock disposal.

6)  use benches-Ans is (O) Because bench is defined as a narrow, strip of land cut into the side of an open pit mine.

7)  best for vein ores -Ans is (O) because they are found in the cracks between the rocks and can be easily obtained by open pit mining.

8) far cheaper-Ans is (O) because more ore can be extracted and more quickly.

9) requires high grades-Ans is (U) because high grades ores generally found deep inside the earth.

Hope you have understood the answer.

Best wishes!