A Quark in OpenRewrite serves as a representation of a file that cannot be parsed, either due to its large size or because it is a type we don't have a parser for (such as images or HTML files). Instead of disregarding such files, we capture their path and relevant metadata (but not the contents of these files). This allows you to move or delete these files in recipes.
If you are running a recipe that is not specifically looking for Quarks, you should never see a Quark.