Macbook air heatsink

Hi
I am a university student and my field is mechanical engineering. I am studying different heat sinks installed on different laptops. As you know most of them are made of copper alloys, look like copper and shine like it but there is a major difference between those and the one, installed on mac book air:

https://www.techrepublic.com/photos/apple-macbook-air-teardown-2010-11-inch/478527?seq=60&tag=thumbnail-view-selector;get-photo-roto

As you can see it is black. Is it painted this way? Does it have miniature fins on the other end? And what is it made from?

Regards
Ali