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The query was prompted by the news that Brazilian football legend Pelé had announced a range of diamonds, each made from a strand of his hair, to commemorate each of the 1283 goals he scored in his professional football career.
It seemed a fairly straightforward request – there’s plenty of carbon in hair and it’s certainly possible to make diamond industrially from a carbon source – so I volunteered to take the call. You can listen to the interview here:
I read around first, to find some extra facts and figures about diamonds. Most of these come from ‘the internet’, as I didn’t have much time before broadcast, so please forgive any inaccuracies.
My search took an immediate, albeit interesting, diversion when I discovered that Pele’s hair is already a known geological phenomenon. Rather than gemstones derived from a footballer’s foliage, Pele’s hair is an extraordinary type of volcanic glass, formed when molten rock is thrown into the air and extruded by the wind into hair-like golden fibres. These fibres travel downwind of the volcano, cool and solidify where they land. These unusual glass structures are named after the Hawaiian goddess of volcanoes rather than the Brazilian godfather of football.
After this brief foray into volcanology, a reworded search confirmed that Pelé really is turning his hair into diamonds, using one of the established techniques for manufacturing synthetic diamond – the high temperature, high pressure, or HTHP method. This is the method that most closely mimics a diamond‘s natural geological formation. As its name suggests, pressures in the vicinity of 7GPa at more than 1700°C are used to grow fairly large stones using a diamond grit seed and carbon dissolved in a molten metal solvent. The exact conditions do vary – one company that makes diamonds from cremains (‘dead dog diamonds’, according to Simon Mayo) uses 5-6GPa at 1600-2000°C. The size of the resulting diamond depends on a number of factors, not least the time for which the conditions are maintained: De Beers once made a 25 carat (5g) stone by holding these conditions for six weeks.
Just in case Simon asked me live on air, I thought I should figure out how big a diamond made from a strand of hair could be, which means estimating how much carbon a single strand of the ex-Santos striker’s hair might contain. Hair is made of a number of different proteins, predominantly keratin, but also contains oils, water and a wide variety of other compounds (hair is routinely used for toxicological or narcotic testing, due to its tendency to accumulate drug metabolites, heavy metals and other toxins). We don’t know what Pelé has been exposed to (if he’s a fan of seafood there may be above average mercury concentration, for example) so I took average values for everything.
An average 12cm human hair (at least in one study) weighs 0.62mg. Making the sweeping assumption that hair contains a nice round 50% carbon by weight, that gives us 0.31mg of carbon from a single strand. If we make another assumption and convert all of that into diamond, we get an unimpressive 0.00155 carat gem. Apparently, each of the Pelé hair diamonds on sale (yours for just £4500) weighs 1 carat. If these gems are pure footballer fuzz, and don’t contain any generic carbon, they would need to be made from around 650 12cm hairs. There are around 100,000 hairs on an average human scalp, so to make the full run of 1283 diamonds, Pelé would need to shave his head completely 8.3 times.
If you’re a committed football fan, these diamonds could be a good investment, and at £4500 are a snip compared to one made from a clip of Beethoven’s barnet, which sold on ebay in 2007 for £121,000.