Dear Dr. Universe: What are crystals? Who discovered them? -Kennedy, 9, Little Rock, AK

Dear Kennedy,

Maybe you’ve caught a snowflake on your tongue. Or sprinkled salt on your food. Perhaps you’ve imagined what it would be like to explore a big crystal cave.

Crystals come in all shapes, sizes, and colors. A lot of them are born from hot magma, deep in the Earth that cools slowly. If you look at a rock, you might even be able to spot some of these crystals.

We can find crystals in nature, but engineers and scientists can also make them in labs. My friend Kelvin Lynn, a materials engineer, is really curious about crystals. He makes them in his lab here at Washington State University.

Lynn explained that crystals are made up of atoms. The atoms are arranged in very particular ways. In order to be a crystal, these atoms have to form a pattern. When scientists see this pattern happening throughout a solid, they call it a crystal lattice.

The opposite of a crystal is what scientists call an amorphous solid. The glass in our windows is one example. It has atoms that are not arranged in a pattern. They are much more scattered than the atoms of a crystal.

Understanding a material’s structure can help scientists learn more how a material behaves, Lynn explained. If it will conduct electricity or heat, for example. In Lynn’s lab, they are curious about how crystals can be used to create power from sunlight.

As for the second part of your question, the idea of crystals and their structures has been around for hundreds of years, Lynn adds. But it wasn’t until about the early 1900s that scientists could get a closer look with X-rays. Sir William Henry Bragg and his son were the first to use this technology to look at the structures of common crystals, including table salt.

I decided to do a little crystal investigation of my own. After whipping up some eggs for breakfast, I had an idea.

I cleaned out the eggshell halves and covered their insides with glue. I sprinkled them with a bit of white powder called alum from the spice section at the store.

I tapped off the extra alum and let the shell sit overnight. The next day, I added some food coloring, about a cup of alum, and two cups of boiling water to a big jar.

Once the water cooled, I pushed the eggshells to the bottom of the liquid. As they sat, alum powder particles falling on the eggshells started attaching to each other.

They began to crystalize. Before long, they looked less like eggshells and more like the sparkling insides of a geode. You can try some science of your own and investigate crystals, too. Just watch the video below to get all the instructions. Tell me about your project sometime or send us a picture at Dr.Universe@wsu.edu.

Sincerely,
Dr. Universe

Special thanks to Jed McCoy at the WSU Center for Materials Research for helping with this question, too.