The process of forming crystals is called crystallization. This happens when liquids start to cool and harden. The molecules gather together by way of electric attraction and arrange themselves in repeating patterns as they attempt to stabilize as a solid.
Crystallization happens in naturally when liquid rock, called magma, cools slowly. Different minerals in magma crystallize at specific temperatures, which separates them into their own distinct crystals. Many valuable crystals, such as diamonds, rubies, and emeralds form this way. If there are gas bubbles in the magma, crystallization can occur in the form of geodes, which we’ll look into later.
Crystals have many unique properties! They can have extremely flat surfaces, called facets, that help make up the geometric shape of the crystal. One interesting property that most transparent crystals have is the birefringence property. This creates a double image when one looks through the crystal, almost like a kaleidoscope! There are seven basic crystal shapes, also called lattices: cubic, trigonal, triclinic, orthorhombic, hexagonal, tetragonal, and monoclinic. The shape a crystal takes depends on the type of molecule/atom that makes up the crystal. For example, pyrite (fool’s gold) often forms cubic crystals!
Most geodes start out as hollow bubbles of gas inside molten rock, but sometimes they can form from the hollow remains of an animal’s burrow or even tree roots! As rain pelts down on a hot bubble of rock, the chemicals in the rock are slowly released into the water. Some of the water soaks through the hard, rocky outside of the bubble and is trapped for a moment on the inside. As the mineral-rich water moves on through the bubble, tiny crystals are left behind, clinging to the sides of the bubble. Millions of years can pass while this flow of water gradually builds more crystals inside the empty space. The crystal formations might become large single crystals or tightly packed micro-crystals, so small that you can’t even distinguish one from another.
- An egg
- A pushpin
- Liquid glue
- A paintbrush
- 1 cup alum powder
- 2 cups of water
- Any color of food coloring
Step One: Carefully wash the outside of the egg you’ll be using to create the geode. Once it’s clean and dry, carefully poke two holes in the shell, one at each rounded end. Use your mouth to blow into one of the holes and push out the insides of the egg.
Step Two: Once the eggshell is empty, cut it in half (lengthwise) using the scissors. Carefully wash the inside of the shell halves with warm water and wipe them dry with a paper towel. Get the inside surface of the shell as clean and dry as possible without cracking it. Peel off and throw away small pieces of shell from around its edge.
Step Three: Drip some glue on the inside of the shell - it’s okay if some gets on the outside too! Use the paintbrush to spread the glue all over the inside of the shell. Completely cover the interior surface with glue all the way up to, and including, the edges. Use more glue if needed.
Step Four: Sprinkle a lot of alum powder on the inside of the shell. Turn the shell-half over and gently tap out any excess alum. Place it on a paper towel or paper plate to dry overnight.
Step Five: The next day, bring 2 cups of water nearly to a boil and pour it into a bowl. Dissolve 30-40 drops of food coloring into the water. Use any color or color combination you wish. Stir it well!
Step Six: Dissolve ¾ cup of alum powder in the hot water and stir well. Let it sit and cool for about 30 minutes.
Step Seven: Once the water has cooled, place the egg shells in the bowl, alum side up. Gently push them to the bottom of the solution with the spoon and allow them to sit there for 12-15 hours. After 12-15 hours, alum crystals have grown! Carefully remove the shells and place them on a paper towel to dry and finish the geode-creation process. Perhaps you can leave them in the bowl longer and see if they grow bigger!
To investigate this further, check out this website!
Bentley, Wilson. “Snowflakes”. Released into the public domain. Uploaded on 4/27/17 from commons.wikimedia.org
Kratochvil, Petr. “Frost on Leaves”. Released into the public domain. Uploaded on 4/27/17 from publicdomainpictures.net
United States Geological Survey. “Rough Diamond”. Released into the public domain. Uploaded on 4/27/17 from commons.wikimedia.org
“Macle of Three-Crystal Pyrite”. Released into the public domain. Uploaded on 4/27/17 from commons.wikimedia.org
Denyer, Circe. “Amethyst Geode”. Released into the public domain. Uploaded on 4/27/17 from publicdomainpictures.net