Fool's gold, iron pyrite, mica... no matter what you call it, at first glance it looks like real gold and sparkles like real gold in the sunlight or when viewed under water, but how do you know FOR SURE if those gleaming flakes are worth something... or exactly nothing?
The quickest and simplest test is to examine your sample in the shade, not in the sunlight. Real gold retains its yellow sheen even in shadow, whereas fool's gold does not.
Also keep in mind that gold is one of the heaviest elements known. Pure gold has a density (specific gravity) of about 19, which means that it weights about 19 times as much as an equivalent amount of water. On the other hand, mica, often mistaken for gold, has a specific gravity of about 2.3. Real gold sinks to the bottom of a gold pan; flakes of mica typically float.
To learn more methods for determining if you have REAL gold, click here.