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Minerals: Color

It may be surprising that the first thing that most people notice about a mineral, its color, is usually not very reliable for identifying it. That is because many minerals occur in a wide range of colors, colored by slight impurities. We can explore that by using a few things from your kitchen.

You will need:


Mud cracks
I took this photo in the wash that runs down the center of our canyon. Not all mud cracks when it dries, and some muds crack more than others. Why?


Cat in snow
This is our newest cat, Little Bit. He is enjoying his first big snow. Is snow classified as a rock? A mineral? Both? Neither?


colorful crystals
I took this photo while working on the "Micro-Crystals" video, and thought this might be a challenge. What common chemical is this? Hint: The colors are from polarizing filters. The crystals are normally clear.


Iron pyrite
This is iron pyrite, also known as "Fool's Gold." While it is not nearly as valuable as gold, it is a very useful mineral. What is it used for?

The Solution to Crystals

Greetings from Hot Springs, Arkansas. Nancy and I have had a wonderful week of digging quartz crystals. The truck is now much heavier, and we are tired but delighted. It was very hard to decide what to do for this week's experiment. I thought about another experiment with retinal fatigue, since all the digging in red clay left us seeing everything with a green hue. I also thought about revisiting the fact that you cannot identify a diamond by cutting glass. The quartz crystals we are digging scratch glass very easily.