The Three Types of Rocks
Free printable types of rocks diagram — igneous, sedimentary and metamorphic rock shown and labeled with how each one forms. Download a high-resolution PDF or PNG for Letter paper.
The three types of rock
Every rock on Earth belongs to one of three groups, based on how it was formed. Here is what happens at each labeled part of the diagram:
| Rock type | What it does | Why it matters |
|---|---|---|
| Igneous | Forms when melted rock (magma or lava) cools and hardens. Often dark and glassy, like cooled lava. | Most of Earth's crust — the ground beneath your feet — started out as igneous rock. Without it, the ocean floors wouldn't exist, and volcanic islands like Hawaii would never have risen from the sea. |
| Sedimentary | Forms when layers of sand, mud and tiny bits of rock are pressed together over a long time. You can often see the flat layers. | Fossils are almost always found in sedimentary rock, because the layering process buries and preserves shells, bones, and leaves before they can decay. Strip away sedimentary rock, and most of the fossil record — everything we know about dinosaurs and ancient life — disappears with it. |
| Metamorphic | Forms when an existing rock is changed by heat and pressure deep underground, often showing wavy bands or stripes. | Marble, one of the most prized building stones in history, is metamorphic — it began as ordinary limestone before heat and pressure transformed it into something harder and more beautiful. The same process that produces marble also builds mountain ranges, squeezing and reshaping rock as tectonic plates collide. |
Companion worksheet
A free fill-in worksheet with an answer key, built from the labels above — students match each rock type to its description, then answer a couple of short questions. Great for a quick check after using the diagram.
How to print
Choose Download PDF for a ready-to-print file that fits US Letter paper (8.5 × 11") in landscape, or Download PNG for the high-resolution image.
Frequently asked questions
What are the three types of rock?
Igneous (cooled magma or lava), sedimentary (pressed layers of sediment), and metamorphic (rock changed by heat and pressure).
How is each type of rock formed?
Igneous rock forms from cooling melted rock, sedimentary rock forms from compacted layers of sediment, and metamorphic rock forms when heat and pressure change an existing rock.
What paper size should I print this on?
The diagram is sized for standard US Letter paper (8.5 × 11") in landscape orientation. Use "Download PDF" for a print-ready file that fits the page automatically.