How to form hydrothermal quartz

How can hot water form beautiful quartz crystals?

This mine is red Georgia clay, with veins of minerals running through it. The veins are hydrothermal. Hydro means water. Thermal means heat. So the veins were caused by hot water. But how could hot water form quartz crystals?

To find out, you will need:
- sugar
- a cup
- water
- something to stir with
- a microwave oven or other heat source

Start by pouring the cup half full (or half empty, depending on your outlook on life) of water. Then start adding sugar. Put in a couple of spoons of sugar and stir until it all dissolves. Add another spoonful, and again, stir until it all dissolves. Keep doing this until you have dissolved as much sugar as you can. Then add another spoonful.

No matter how much you stir, that last spoonful is not going to dissolve, unless we make a change. Lets heat the water. Put the cup into the microwave oven, and heat it for about 30 seconds. Carefully remove the cup and stir. You should find that most, if not all of the sugar will now dissolve. If it does not, put it back in for another 30 seconds, and try again. Be sure to stir the water and sugar every 30 seconds.

Once the water is hot, you can add another spoon of sugar, and it should also dissolve. As you get the water hotter and hotter, it can dissolve more and more sugar. It will also dissolve more and more substances, but it still won't dissolve quartz. Long before the water is hot enough to dissolve quartz, it reaches its boiling point.

You can raise the boiling point by increasing the air pressure. That is how a pressure cooker works. The sealed pressure cooker builds up pressure from boiling water, which raises the boiling point. That lets you cook foods faster, because the water gets much hotter than 212 degrees Fahrenheit.

Okay, so where did the tremendous heat and pressure come from to dissolve the quartz in these rocks? Magma. Magma is molten rock that is still underground.