Ask-a-Geologist #20: What can you tell me about the mineral pyrite?

Tell me about the mineral pyrite.

Today I have a special guest with me on the Mini Me Geology Ask-a-Geologist videl. Her name is Piper and we are discussing the mineral pyrite.  (Make sure you watch the video until the end to see our first blooper reel!)

Piper: I got this pyrite sample as a gift. Can you tell me about it?

The mineral name “pyrite” comes from the Greek word for fire. People believe that pyrite got its name because it will spark when you hit it with a steel hammer.

Pyrite is a mineral that is most often known as “fool’s gold” because it looks like real gold. Do you know how to tell the difference?

Piper:  No. How do you tell them apart?

Pyrite Mineral Sample

There are two ways that you can tell them apart. One is the hardness of the samples, and the other is the weight of the samples. Now hardness basically tells you where a mineral is on the Mohs hardness scale. Gold is really, really soft. It’s about a 2.5 to 3 on the scale, which goes from zero to 10. And pyrite is about a 6 to a 6.5 on the scale.

If you had a sample of gold, you could actually take a hammer and pound it out and make it flat. Pyrite, it’s not as easy to do that. Something else you can use is a penny that is older than 1982. Older pennies are in the middle of the Mohs scale. So what you can do is take the penny and scratch it on your sample. If it scratches your sample, you probably have gold because gold is softer than an old penny. If you can’t scratch the sample, and no scratch appears on the sample, it is most likely pyrite. That is because the pyrite is harder than the penny.

The other way is to check out the weight of the sample, and while the sample that Piper has is pretty big and it feels kind of heavy in your hands if you had an equally sized piece of gold, it would be much, much heavier. So pyrite is a lot lighter in weight than gold. Now I’m going to show you something really interesting about Piper’s sample. Pyrite can form a lot of really neat shapes. You look right here on the top of Piper’s sample, you can see that it has different shapes like cubes and octahedrons, and sometimes you can also see that there are little scratches known as “striations” on the faces of the cubes, and that is really characteristic of a pyrite sample. Is there anything else that you want to know about your sample?

Piper: What can I use my pyrite for?

Well, some companies use pyrite to make sulfuric acid, but you don’t need any of that. A beautiful sample like this is best in a collection like yours.

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