Purifying Sand

There are many grades of sand. I’m learning this from Ed Conway’s Material World where sand is the first of “the six raw materials that shape modern civilization”. The story begins with glass. Pliny the Elder claims it was the Phoenician sailors and traders who, in the evening, “lit a fire on the beach, and in the absence of anywhere else to rest their pots, they perched them on some of the natron blocks”. Natron is rich in sodium carbonate, and combined with seashore sand and high temperatures, makes glass. Or at least a type of glass. There are many different types.

 

Glass is mostly silicon dioxide (SiO₂), commonly known as silica. But it has a very high melting point, and will only melt in a simple open furnace if impurities such as sodium are present, because these impurities lower the melting point – as my G-Chem students have learned. But this also affects the quality and type of glass produced. Now if you can find sand that is over 95% silica, you can make useful stuff such as water filters, or you can make “the very clearest, finest glass”. There are some specific locations around the world, and Conway discusses a visit to Scotland to a rock mine with 99% pure silica. Conway then tells a fascinating story about the importance of field glasses (binoculars) requiring really high-quality glass and the key role they played in the first world war. Call it the early tech information support that is crucial! Nowadays we use satellites and drones.

 

Concrete is the second product of sand that Conway discusses. I had previously read about the Roman aqueducts and the discovery of Portland cement so much of this chapter was familiar. But Conway also discusses land reclamation projects all over the world, and I was staggered by how much earth has been moved both to make concrete for buildings, and to make new ground where there once was sea to place such buildings. I learned about governments playing cat-and-mouse with “sand mafia” gangs who would perform bloody murder to keep their illegal trade going. Conway also discusses new concrete-like materials that have a lower carbon footprint. Some are based on hemp. Some on graphene. And there’s even one designed to absorb carbon dioxide over time.

 

Most eye-opening to me was the production of ultra-pure silicon. It needs to be 99.9999999% pure to be nanocrystal-grade. You need it for your latest and greatest computer chips that are powering the A.I. revolution. Conway traces the supply chain, from raw materials, to multiple factory-industrial stages, before you get those Nvidia or AMD branded ones that are in high demand. The manufacturing process is so demanding that I was in awe of everything that has to go right when so many things that can go wrong. And these companies in the supply chain have perfected the techniques for mass production. They are all over the world and except for TSMC and ASML that have been in the news recently, I hadn’t heard of the many others that Conway listed. All of them are crucial cogs and the supply could easily be cut off. Scary, now that we’re so dependent on computer chips in everything.

 

Reading Material World reminded me of how I’d like to re-theme my G-Chem class to focus on materials. I haven’t figured out exactly how to do that yet, but I have some fresh ideas to chew on. Up next in my reading: Salt.