# The Most Dangerous Rock In Hannah's Collection

An episode of [The Rest Is Science](https://invisiblenetwork.ai/podcast/1853007888), 1 Jul 2026, 56 min.

Audio: https://pdst.fm/e/traffic.megaphone.fm/GLT9057021187.mp3

When you think of dangerous geological specimens, does your mind jump straight to radioactive uranium, toxic heavy metals, or even asbestos? What if one of the most dangerous items sitting on a shelf is actually a polished, perfectly ordinary-looking piece of black obsidian? Professor Hannah Fry and Michael Stevens dive into the surprisingly treacherous geology and chemistry of obsidian. Hannah brings an onyx from her personal rock collection to explain exactly why this specific piece of material holds the title of the most dangerous rock she owns, unpicking the fascinating physical properties of the stone and exploring how its conchoidal fracture pattern can easily create edges sharper than a modern surgical scalpel. ------------------- For more information about Cancer Research UK, their research, breakthroughs and how you can support them, visit https://cancerresearchuk.org/restisscience Cancer Research UK is a registered charity in England and Wales (1089464), Scotland (SC041666), the Isle of Man (1103) and Jersey (247). A company limited by guarantee. Registered company in England and Wales (4325234) and the Isle of Man (5713F). Registered address: 2 Redman Place, London, E20 1JQ. ------------------- Find The Rest Is Science all over the internet by clicking here. ------------------- Video Producer: Adam Thornton + Oli Oakley + Jack Meek Animator: Sam Benson Video & Social: Bex Tyrrell Assistant Producer: Lucy Lipscombe Producer: Simona Rata Senior Producer: Lauren Armstrong-Carter Head Of Digital: Samuel Oakley Exec Producer: Neil Fearn Learn more about your ad choices. Visit podcastchoices.com/adchoices

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