Penelope Clearwater's mirror was a mirror belonging to Penelope Clearwater.
The mirror was used by Penelope to look around for Slytherin's Basilisk. Hermione Granger also looked through it and they saw the Basilisk and they ended up getting Petrified and did not die because they saw the Basilisk through the mirror and did not look into its eyes.
Behind the scenes
- In the film adaptation of Harry Potter and the Chamber of Secrets, as Penelope was not a victim of the Basilisk and it was only Hermione who was petrified, the mirror Hermione had did not seem to belong to Penelope.