Pyrite

Pyrite has a nickname more famous than its name: "fool's gold". Its brassy color and metallic luster fooled plenty of beginner gold prospectors, and that is how the nickname was born. The photo shows a raw lump covered all over in small cube-shaped crystals, each one throwing the light in a different direction. According to Wikipedia, pyrite usually forms cubic crystals, and sometimes twelve-sided shapes too.

The name comes from the Greek word for fire, "pyr", because if you strike pyrite against metal or hard stone, it throws sparks. And that is more than a pretty name. According to Wikipedia, the oldest definite evidence of fire making, from about 400,000 years ago, was found at a Neanderthal site in England, together with two fragments of pyrite used to strike sparks with flint. Ötzi, the Iceman who lived more than five thousand years ago, carried flint, pyrite and a tinder fungus. In the 16th and 17th centuries, pyrite was also used to fire early guns.

Now for the awkward part of the nickname: according to Geology.com, pyrite and gold often form under the same conditions and in the same rocks, and some pyrite contains enough gold to be worth mining, sometimes a quarter of a percent of its weight or more. So whoever found pyrite may not have found gold, but they might be standing right next to it. Telling them apart is easy: gold is soft and bends, and pyrite is brittle and breaks. Rub them on an unglazed porcelain tile, and gold leaves a yellow streak, while pyrite leaves a greenish black one.

In the Victorian era, pyrite was a fashionable jewelry stone. According to Geology.com, most of the jewelry sold then as "marcasite" was actually pyrite. It has just one weakness: moisture. According to Wikipedia, pyrite exposed to air and water slowly breaks down and releases sulfuric acid. So keep it somewhere dry.

It has a local chapter too. According to Hebrew Wikipedia, in 1930 an Englishman named Leonard Lloyd Williams was licensed to produce sulfur south of Gaza, and at depth he found veins containing pyrite. The mine was abandoned, and the site is known today as the Be'eri sulfur quarries.