It's possible you're thinking of:
* The Black Mountains in New South Wales: These are actually called the Black Range and are a mountain range with dark-colored, weathered sandstone giving them their name. The sandstone is usually a reddish-brown color but can appear darker due to weathering and the presence of iron oxides.
* The Black Mountains in Western Australia: This is a less well-known area with similar dark-colored rock formations, also likely due to weathering and the presence of iron oxides in the sandstone.
* The Black Mountain in Canberra: This is a prominent hill in the Australian capital, composed primarily of granite. While not technically black, the granite can appear dark due to its composition and weathering.
In summary: The "blackness" of these Australian mountains is primarily due to weathering and the presence of iron oxides in the rock. While there are no true "black mountains" in the geological sense, the term is used to describe areas with dark-colored rocks due to weathering and composition.
