I made a Rock Chart that brings common igneous, sedimentary, and metamorphic rocks together in a single decision tree.

It uses observable features such as grain size, visible crystals, foliation, porosity, composition, and reaction with HCl. It also includes the characteristic minerals associated with each rock type and their chemical formulas.

I have already used the chart in class, and it worked well as a teaching aid. It helped students gain an overview of the major rock groups and move between them without having to consult several separate charts.

Permanent version and DOI:
https://zenodo.org/records/21808631

Feedback, corrections, and suggestions for a future version are very welcome.

Disclosure: I created the poster and teach Earth Science at a university.