Modelling crystal structure using marshmallows

By Stephen Ashworth2014-07-01T11:55:00

Enormous gypsum crystals in a Naica cavern, found during mining; the silhouette of a miner in the bottom right provides scale

Explore the regular and ordered structure of crystals before modelling them yourself using marshmallows and cocktail sticks in this ‘Avogadro’s lab’ activity.

Crystals are beautiful. The word ‘crystal’ may first bring to mind gemstones, whose rarity and appearance make them very precious, but there are exquisite crystals all around us. Salt and sugar can both form crystals, as can ice. Under the right conditions crystals can become very large indeed. A working mine in Naica, Mexico, hosts the largest crystals in the world. They are crystals of the mineral gypsum (calcium sulfate(VI)-2-water), and some are over 11 metres long and weigh 50,000 kg.

Read on to try modelling the structure of crystals yourself using only marshmallows and cocktail sticks.

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