What type of skin is described as "extremely dark" and often found in Aboriginal populations?

The description of "extremely dark" skin aligns with what is classified as skin type 6 in the Fitzpatrick skin typing system. This type of skin is characterized by a high concentration of melanin, providing significant protection against UV radiation. Individuals with skin type 6 typically do not sunburn and have a natural ability to tan, which is often associated with populations in parts of Africa, the Pacific Islands, and certain Aboriginal groups. This classification emphasizes the skin's resilience to sun exposure due to its natural pigmentation.

In contrast, the other skin types do not describe the "extremely dark" characteristic as effectively, with lighter skin types being more susceptible to sunburn and having less melanin, thus falling short of the description required in the question.