Gold — The Lithotheque — Seek With What

Why it is that colour

Genuinely unusual physics. Most metals are silvery because they reflect all visible wavelengths; gold absorbs blue light, and the reason it does involves relativistic effects on its innermost electrons, which move fast enough that Einstein has to be taken into account. Gold is yellow because of relativity.

Safety

Metallic gold is biologically inert, which is why it is used in dentistry and implants. Some gold compounds are toxic, and gold mining is another matter entirely: artisanal gold extraction using mercury amalgamation is the largest single source of mercury pollution on earth.

Where it comes from

Extremely difficult ethically. Large-scale mining moves enormous quantities of rock for small yields and uses cyanide leaching. Artisanal and small-scale mining employs perhaps fifteen million people, uses mercury on a huge scale, and is associated with child labour and with conflict financing in several regions. Recycled gold is the only straightforwardly clean source.

Historical use

The metal that shaped monetary systems, colonial expansion and a great deal of violence. Roughly all the gold ever mined — around two hundred thousand tonnes — still exists, because it does not corrode and nobody throws it away.

Recorded as history and attributed where possible. That a stone was used for something establishes that people used it, not that it worked.

What is attributed to it, and since when

Universal and ancient. Gold is the sun in the alchemical scheme of seven metals and seven planets, the perfected metal that all others aspire to, and the goal of transmutation. Its associations with sovereignty, divinity and incorruptibility appear independently across most literate cultures, and they follow from a real property: it does not tarnish.

Described, not endorsed. Dating a claim is not the same as assessing it — but an association that first appears in a book published in 1985 is not an ancient inheritance, whatever the label says. A sincere account of feeling better is compatible with the stone doing nothing — see the placebo effect.

Worth knowing

Gold is yellow because of Einstein, and this is not a stretch. In a heavy atom the innermost electrons orbit fast enough that relativistic effects contract their orbitals, which shifts the energy gap that governs which light the metal absorbs. In silver, the gap is large and all visible light is reflected. In gold, relativity narrows it enough to absorb blue. Do the calculation without relativity and gold comes out silver.

Its inertness is the whole of its reputation. A metal that never tarnishes, never rusts, and can be buried for three thousand years and dug up bright is going to be understood as incorruptible, and every tradition that encountered it reached that conclusion independently. Alchemy's project follows directly: if gold is the perfected state of metal, then base metals are gold that has not finished becoming itself.

The environmental arithmetic is grim. Artisanal miners use mercury to amalgamate gold from ore and then burn it off, releasing it directly into air and water. UNEP has identified this as the largest anthropogenic source of mercury emissions in the world.