We start with the heavyweight family. If you want copper, lead, zinc, or nickel, you're usually looking at a sulfide.

The definition: a sulfide is a mineral where the metal is joined to sulfur (chemists write sulfur as the letter S). Sulfur is the partner element — that's the whole reason the family has this name.

The star minerals

• Chalcopyrite — the world's number-one copper ore. (It contains iron too, but copper is the prize.)
• Galena — the main ore of lead, and it often carries a little silver as a bonus.
• Sphalerite — the main ore of zinc.
• Pentlandite — a major ore of nickel.
• Pyrite — "fool's gold." Usually it's waste, not the metal anyone's after.

How they form and how we mine them

Sulfides usually form from hot fluids and magma deep in the Earth's crust. That means they tend to sit deep, so they're mined underground or in big, deep open pits.

How we get the metal out

Sulfides have a friendly trick: their grain surfaces can be made to repel water, so they cling to air bubbles. That makes flotation the perfect first step — crush, add chemicals, and float the valuable grains off. After that comes smelting, where heat melts the metal out and burns off the sulfur.

One historical note: burning off all that sulfur releases sulfur-dioxide gas, which used to cause acid rain. Modern smelters capture it and turn it into sulfuric acid instead of letting it escape.