Which of the following is a natural resource mined in Western Australia?

Western Australia is renowned for its rich deposits of minerals and is one of the world's leading producers of gold. The state has a long history of gold mining, with significant goldfields located in areas such as Kalgoorlie and the Eastern Goldfields. This makes gold a prominent natural resource extracted in the region.

Copper, while present in Western Australia, is not as significant a contributor to the state's mining industry as gold. Aluminum is primarily produced from bauxite, which is more prevalent in other regions rather than being a primary focus in Western Australia. Similarly, silicon mining is not a major industry specific to the region when compared to gold production. Gold stands out as the most significant and historically important mineral resource mined in Western Australia, which is why it is the correct choice.