Barbara Wood, age 11, of Newtonville, N for her question;

What is fool’s gold?

In ancient days they had a more sensible name for this mineral. They called it pyrite, meaning fire stone. A lump of it is hard enough to strike sparks and start a fire. Before the invention of the tinderbox or the match, a lump of pyrite was a very valuable possession. And even today, pyrite is a valuable mineral. No sensible prospector passes up a rich vein of fool's gold.

Pyrite is a mineral composed chiefly of iron and sulphur. It may be iron disulphate or iron pyrite. As you guessed, it looks like gold. Flakes of it occurring in gold bearing quartz rocks have fooled many a prospector. Pyrite, however, is much harder than gold. It rates in class six on the scale of mineral hardness. The diamond, hardest of natural minerals, rates in class 10 and talc, one of the softest minerals rates in class 1. Gold is rated 2.5 on the mineral scale of hardness.

Pure gold will not tarnish. But pyrite tarnishes in heat and maybe even in the air. Gold is soft and pliable under a hammer blow. Pyrite is brittle and breaks under the hammer. These are a few simple tests by which a prospector can tell real gold from fools gold.

Pyrite is a plentiful mineral and occurs in rocks of all sorts. It occurs in papery layers throughout slates, shales and even coal. Lumps of it occur in fire formed rocks and flakes occur in beds of quartz.

Though basically pyrite is a compound of iron and sulphur, it usually contains other minerals. A compound of copper and iron pyrite is chalopyrite, a valuable copper ore. It is somewhat more yellowish in color than iron pyrite and tends to tarnish with rainbow colors. Pyrite is also found in combination with nickel, cobalt, lead, zinc, arsenic and gold.

Real gold is very often present in rocks that show pyrite. It may occur in invisible particles, but sometimes there is enough of it to make it Worthwhile to mine fool's gold for its real gold content.

The world mines almost five million tons of iron pyrite every year. There must be a reason for all this hard work   and so there is. Pyrite is mined for its valuable sulphur content. Most of it is processed to make sulphuric acid.

We do not meet sulphuric acid in everyday life. Its work is done behind the scenes. Millions of tons of it are produced for industry every year. Even so, some of this vast quantity is re used. The sulphuric acid used in rayon manufacture may be salvaged and used as soil fertilizer.

Sulphuric acid plays a role in the manufacture of thousands of common items, It is used in the refining of petroleum in certain steels, in dyes and certain textiles. It plays a role in certain printing processes, in the manufacture of soap, glue and even gelatin. And a good deal of this supply of valuable sulphuric acid comes from iron pyrite   the so called fool's gold.