Tuesday, 4 August 2009

Twisted metal

One of the things I get asked about a lot in the shop is bismuth. Bismuth is an elemental metal that's grouped with arsenic and antimony. Unlike those, however, it's not (very) poisonous. In fact, one of it's main uses until relatively recently has been in stomach medicines for various reasons. Pepto-bismol, for example.

It forms naturally in a couple of ores and sometimes as nuggets. What draws the comments and questions, though, are the artificially grown hopper crystals. These are made using almost completely pure bismuth with trace additions of other elements to add varied colour to the oxidised layer that quickly forms over the silvery-grey surface.

Only a few people in the world make it, and the process to make decent crystals is a closely guarded secret. A friend of mine bought the business and know-how from a retiring Belgian and is now making his own in his garage in England. A few experiments has led him to the biggest crystals ever made. It's pretty brittle stuff, so once the crystals get over a certain size they can be quite fragile. He buys the raw material in ingots from a company that refines metals. The price has risen a fair bit in recent years as bismuth has gone from being a moderately useful by-product to an increasingly important product in its own right.

It's now being used as a substitute for lead in fishing weights, as an alloy for shot, pellets and plumbing uses. There are plenty of other new uses, but an important discovery made recently will lead to it being used in electrical circuit boards and in solar power cells. Bismuth diodes allow
two-way current flow, which will create far more efficiency in electrical equipment.

Great for global technology, not so great for the price of bismuth crystals.

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