I teach my students that there are "buzz words" that should help them know what type of rock we are learning about. In this activity, students have to sort the buzz words under the correct rock type.
Once my students have learned these buzz words, they are able to identify rocks and talk about them using appropriate science vocabulary. It also helps them on test to pull out buzz words in questions.
I use this activity as a cut and paste but it could be used as a sorting activity with laminated cards as well.