Gold vs Silver

Silver is the better metal at nearly every physical job. It carries more current, moves more heat and throws back more light than any other element on the table. Gold beats it at exactly one thing, and that one thing is enough to decide most real choices: gold does not tarnish.

That is the whole comparison in two sentences. Everything below is about how much the tarnish costs you, and when it costs you nothing at all.

The one weakness that reorganises everything

Silver does not rust and it does not oxidise in air at room temperature. What blackens it is sulfur — traces of hydrogen sulfide and carbonyl sulfide in ordinary air, which convert the surface to silver sulfide over months. The film is thin, but it is a poor conductor, and on any surface that has to make electrical contact at low voltage it is fatal. A signal that arrives at a connector with a few milliamps behind it cannot punch through a sulfide layer.

Gold has no such reaction available to it. It is indifferent to oxygen, water, sulfur and every single acid; only a mixture such as aqua regia, or a cyanide solution in the presence of air, will take it into solution. A gold surface plated in 1975 makes the same contact resistance today that it made then.

Why connectors are gold and switchgear is silver

The received wisdom that "gold is used because it conducts well" is wrong, and the truth is more interesting. Gold is the third-best conductor of the elements, behind silver and copper. Nobody plates a pin in gold for its conductivity — they plate it because the contact resistance stays put.

So the two metals split the electrical world by current, not by prestige:

• Low-voltage, low-current, must-not-drift contacts — edge connectors, IC package leads, card slots, aerospace and medical connectors — are gold, in coatings measured in fractions of a micrometre over a nickel barrier.
• High-current contacts — relay contacts, contactors, circuit-breaker tips — are silver and silver-oxide composites, because at tens or hundreds of amps the arc burns any film off anyway and what matters is bulk conductivity and resistance to welding shut.

Gold's other electrical niche is thermal as much as electrical: gold bonding wire inside chip packages, though cost pressure has pushed much of that to copper.

Two metals pointed at different parts of the spectrum

Silver reflects better than 95% of visible light across the whole range, which is why an ordinary household mirror is silvered — and safe to silver, because the coating is sealed behind glass and never meets air.

Gold reflects visible blue light poorly, which is precisely why it looks yellow, but in the infrared it is close to perfect and it stays that way without a protective overcoat. That combination is why the James Webb Space Telescope's eighteen beryllium segments are gold-coated, about 100 nanometres thick, using something under fifty grams of gold in total. Observatories working in visible light coat their mirrors with aluminum instead and recoat them periodically.

Karats, sterling, and the part that wears off

Purity is the first assumption to drop. Both metals arrive at a customer already alloyed, but the motives are opposite: silver is cut to make it hard enough to survive being handled, gold is cut to bring the price down and to move the colour.

Sterling silver is 92.5% silver with the balance usually copper, and it is the copper, not the silver, that drives most of the discolouration people complain about. Gold jewellery is quoted in karats out of 24: 18k is 75% gold, 14k is 58.3%. White gold is gold alloyed with palladium or nickel and then plated with rhodium, and the rhodium is a consumable — it wears through and gets redone, which is a maintenance cost people are rarely told about at the counter.

Leaf is where the difference stops being cosmetic. Both metals beat out into film thin enough to handle only with a brush, but silver leaf oxidises and has to be sealed under varnish to keep its colour, whereas gold leaf applied to a dome a century ago is frequently still the metal that was laid there. What a gilder pays for is that permanence rather than the thinness.

The ratio moves, and the reason is on the demand side

Quoting a price here would be stale within weeks, so the useful number is the relationship. The gold-to-silver ratio sat near 15 to 1 under the old bimetallic coinage standards, averaged something closer to the mid-tens-of-ones through the twentieth century, and briefly exceeded 100 to 1 in early 2020. It is not anchored to anything physical.

The structural reason silver is the more violent of the two prices: roughly half of silver demand is industrial, and photovoltaic cell metallisation has become one of its largest single sinks, so silver tracks the manufacturing cycle in a way gold does not. Meanwhile most silver is not mined for its own sake at all — the majority arrives as a by-product of lead, zinc and copper operations, which means the supply barely responds when the silver price moves. Inelastic supply plus cyclical demand is a recipe for a jumpy market. Gold, mined deliberately and held largely as a monetary asset, behaves like a different asset class entirely.

Inside the body, and against bacteria

Silver ions are genuinely toxic to bacteria at low concentrations, which is the basis of silver wound dressings and silver-loaded catheters. The same chemistry has a cosmetic consequence when silver compounds are ingested over long periods: argyria, an irreversible slate-grey discolouration of the skin caused by deposited silver.

Gold is biologically inert almost to the point of being boring, and that inertness is its medical value. Gold-alloy dental restorations wear at close to the rate of natural enamel and provoke no reaction from surrounding tissue. Gold salts were a standard rheumatoid arthritis treatment for decades before better drugs arrived.

Tarnish or conductivity: pick the one you can live without

• A contact that must still work in twenty years at signal-level currents — gold, plated, with no substitute worth discussing.
• A conductor where cost per amp is what matters — neither; use copper, and reach for silver only where the last few per cent of conductivity justifies the price.
• A reflector for infrared that will sit exposed — gold.
• A reflector for visible light behind glass — silver.
• An everyday ring on a hand that sweats — gold, or accept that silver will need cleaning.
• A bet on industrial demand — silver, with the volatility that implies.
• A store of value that ignores the factory cycle — gold.

The honest summary is that they are not really rivals. They compete only in jewellery cases, where the decision is aesthetic and the metallurgy is a footnote.