What are three examples for the root word petra?

Here are three examples of words using the root "petra" which means "stone" or "rock":

1. Petrified: This word means "turned into stone" and is often used to describe wood or other organic material that has been fossilized.

2. Petroglyph: This word refers to a carving or inscription made on rock. It's often used to describe ancient rock art.

3. Petrologist: This word describes someone who studies rocks and their formation.