I used worsted weight Malabrigo Rios in color Jupiter. I can't say enough about how much I loved working with this yarn. Rios is incredibly soft and springy, and the colors are amazing. Jupiter has a range of cool reds with bits of green and very dark brown. I can't wait to work with it again!
Installing a zipper might be a bit more fiddly than buttons, but I love zip-front cardigans. My pattern includes a tutorial for sewing in the zipper.
You can learn more about Lava Rock Cardigan on the Ravelry pattern page, or just: