Jim slacker, ago 11, of Indianapolis, Ind., for his question:

What is fool’s gold?

This shiny yellow mineral has foiled many a gold prospector. But if the rockbound knows his minerals, he does not stay fooled for long. Fool’s gold may look like real gold but it does not behave like real gold.

The proper name for this tricky mineral is iron pyrite. It is an iron sulphide, a compound of iron and sulphur. It melts easily, giving off sulphuric fumes, end may become magnetic, pyrite is abundant in the earth and may occur in any type of rock in any type of vein. When moist, it tends to give off sulphuric acid and this may turn surrounding limestone into pyrite seams to enjoy confusing the prospector. For it frequently occurs in and near deposits of real Gold. In fact, it is sometimes mined for the gold scattered through it. It may be found in flakes or nuggets. The smart rockbound tests it for hardness, for pyrite is much harder than gold. Gold is soft and malleable and tends to bend rather than break. Pyrite is hard and brittle and tends to crack and break under pressure and, when heated, pyrite gives off sulphur fumes and gold does not.