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Phrases and Idioms
Iron pyrite is a mineral that bears a resemblance to gold, but in terms of value, it does not compare; hence its been given the nickname "fool's gold."
This phrase comes from the fact that there is a mineral that looks similar to gold in appearance, and as a result, it fools many people. As an example, look at what happened to an English seaman by the name of Martin Frobisher. During the second half of the 16th century, he made three trips to Canada. On his second trip he found a mineral that he thought was gold and so he carried hundreds of tons of the stuff back home with him on three ships, where he made a fine profit.

Intrigued, Frobisher returned to Canada with several additional ships than he had before in order to mine and carry even more of this "gold" back with him, and that's exactly what he did. After years of smelting, eventually it was figured out that this wasn't gold at all, it was actually just a worthless (in terms of value) mineral known as iron pyrite.

The phrase makes an early appearance in 1872, where an article entitled "Fool's Gold and How we may Know it," is found in the Indiana Progress newspaper. There it reads:

"There are several minterals which are sometimes mistaken for gold, but the two which are most apt to
give rise to deception in this matter are pyrites and mica, and hence they are sometimes called fool's gold."

Reference: Wikipedia - Martin Frobisher and newspaperarchive had the newspaper containing the idiom in the quote above.
Common Phrase Origins and Meanings > F-Letter Sayings
Note: The phrase origins, or history of particular idioms can be difficult to trace down, so finding the precise time a saying came into existance is no walk in the park. What you will usually find on this site are moments in history where an expression started to be used on a widely-known basis.
For instance, a lot of popular sayings can be spotted in old newspapers from several decades ago, but think about that for a second. If an idiom is being used in the media, it seems apparent that everybody already knows about it! What does that mean? Well, it means the origins of the phrase are probably much older.

On this site, what you'll typically find are early usages of particular expressions, usually coming from aged books, plays, poems, or newspapers. It's meant to give you an estimate on how long certain phrases have been used for, but not necessarily where they originated from.
* Being short of cash, I decided to buy my wife a ring made out of fools gold rather than the real thing. I don't think she'll mind, really.
Phrase Meaning for Fish Out of Water.
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