Which 4 of the following are True?

1. Most coal in NZ is extracted using open cast methods
2. Open cast mining is more expensive as it uses large machines
3. Open cast mining is more efficient than underground mining
4. Open cast mining can only occur if the coal is of good quality
5. Open cast mining is safer than underground mining
6. Open cast mining needs more skilled workers
7. Open cast mining has only been possible with an increase in technology

Which 4 of the following are or have been open cast mines?

1. Stockton mine
2. Strongmans mine
3. Rotowaro mine
4. Weavers' mine
5. Huntly East mine
6. Huntly West mine
7. Ohai
8. Spring Creek