As with learning to understand anything, it’s often easiest to learn by doing. This is the same for understanding how crystals form. Making rock candy is an easy way to do this.
Rock Candy Recipe
Rock candy is simply crystallized sugar. Here’s our recipe:
- Take a pot of water and stir in as much sugar as you can.
- When you see it settling on the bottom and no more dissolves, you have reached the saturation point. The water has absorbed all the sugar it can and this condition is called super-saturated.
- Next, bring the pot to boil (at boiling, saturation changes, and you can add more sugar).
- Add more sugar until you hit super-saturation again.
- Remove the pot from the stove.
- As the water cools to room temperature, the water can no longer hold the higher amount of dissolved sugar. The excess sugar will re-solidify out of the liquid, and crystallize.
- Hang a string or place a stick in the sugar solution for the crystals to grow on. They won’t grow fast enough to watch in real time, but checking every few minutes will show the change.
- When fully cooled, the string or stick will be covered with sugar crystals.
A primary principle of crystallization is that as a liquid temperature goes down, so does the volume of dissolved solid ingredients it can hold. Sugar is a much simpler ingredient than found in the Earth. When crystallizing sugar, you will always get sugar. In the Earth, the varying temperatures may result in different minerals crystalizing from the same mixture of ingredients. For example, topaz could be the first crystal to form, followed by quartz.
Five things are needed for crystallization:
The rock candy required no pressure to form but it takes the proper combination of pressure and temperature for minerals to crystallize.
Time and space are easy to come by, but the mixture of ingredients, heat, and pressure require more precision.
This formula leads us to How Gemstones are Formed.