What is one main theme in the novel, King Solomon’s Mines?

Given the historical period in which the novel was written, it is noteworthy that Quatermain respects integrity, honesty, and bravery as much in black Africans as he does in his white associates. In fact, one of the novel's major themes seems to be that such virtues transcend race, and that heroism is heroism, no matter what the color of one's skin.