杏吧原创

Pyrite power: did it help beget the modern technological world? (Image: John Cancalosi/National Geographic Creative)

鈥淏Y NO mineral substance have men been more deceived, than by iron pyrites; which is very appropriately denominated fool鈥檚 gold.鈥� With these harsh words in a bestselling 19th-century textbook, the eminent geologist Edward Hitchcock summed up the shady reputation of FeS₂, a shiny golden crystal that is common throughout the world.

Hitchcock had a point. Pyrite was a favourite of alchemists, who sought to transmute it into gold. It was popular with explorers, too, who used pyrite 鈥渢reasure鈥� to bamboozle investors. Yet there are also myriad admirable facets to fool鈥檚 gold, and in Pyrite, geologist David Rickard puts himself forward as the mineral鈥檚 foremost advocate.

Rickard鈥檚 esteem is boundless: 鈥淧yrite has had a disproportionate and hitherto unrecognized influence on developing the world as we know it today 鈥� This influence extends from human evolution and culture, through science and industry, to ancient, modern, and future Earth environments and the origins and evolution of early life.鈥�

鈥淧yrite was popular with explorers, who used it as 鈥榯reasure鈥� to bamboozle investors鈥�

That鈥檚 a big claim for any substance. To Rickard鈥檚 credit, he largely justifies it. The importance of pyrite to prehistoric and ancient peoples is preserved in its name: pyrite means 鈥渇ire stone鈥� in ancient Greek. Fires were set by striking pyrite against a flint, producing a spark hot enough to ignite dried twigs. The mineral was also a source of pigments such as red ochre, which is produced when pyrite oxidises in aerated water. Pyrite may even have been the first non-herbal medicine: when burned, it emits sulphur oxide gases that can clear sinuses when inhaled.

Based on these worthy uses, Rickard provocatively observes that the first mineral sought by ancient prospectors may not have been the 鈥渆xotic鈥� gold and silver of later civilizations but pyrite. It is pure speculation, but plausible.

The mineral is certainly sought after by modern scientists. One of pyrite鈥檚 remarkable attributes is its sheer variety of crystals. By one count, there are nearly 700 different shapes, or 鈥渉abits鈥� 鈥� possibly the greatest range in any common substance.

Because different crystal habits are caused by different geological conditions, and because microscopic pyrite crystals are nearly ubiquitous, Rickard argues that much of what we know about the history of Earth has come from investigating ancient pyrite. He gives many examples, and his first-hand knowledge makes this the strongest part of his book. For instance, he describes how pyrite crystals that formed around ancient deep-sea vents have been used to map volcanism and to measure planetary cooling.

His own research has been key here. In particular, his team has studied variables, such as hydrodynamics and pH, that affect crystals in the field and then used them to create 鈥渄esigner pyrite鈥� in the lab. And Rickard makes a forceful case for the importance of this science for environmental modelling and prediction.

He also notes the part that pyrite may play in green technology, especially solar power. Like the silicon used in conventional solar cells, pyrite is a semiconductor but, he says, it 鈥渁bsorbs 100 times as much light鈥�. And it is ultra-cheap, too.

Such claims astound 鈥� even Hitchcock would be impressed 鈥� but Rickard gets carried away. The mineral, he asserts more than once, 鈥渕ade the modern world鈥�, and improved our 鈥渜uality of life鈥�. He adds: 鈥淧yrite is the universal common ancestor of technology.鈥�

A touch too close to his subject perhaps? An equally good case could be made for oxygen or water.

That said, Rickard鈥檚 book is an essential corrective to pyrite鈥檚 fool鈥檚-gold reputation. In fact, pyrite has even begun to show its worth to gold prospectors. Most gold mined today is in the form of microscopic blebs trapped inside minerals. Ironically, pyritic ores are the richest source.

This article appeared in print under the headline 鈥淲ho鈥檚 the fool?鈥�