What's In The Mineral

Before we begin discussing minerals and crystals, let's take a look at actual silver crystal growth in real time.

We are going to actually watch silver crystals grow in real time in a microscope.

  • You will need microscopes for each group of students.  
  • Cut 1 inch of copper wire and place on a petri dish under the microscope.
  • Add two drops of silver nitrate on the copper.
  • Observe the results.  Try observing using two different magnification.

If you missed this demonstration you can watch the following video.

silver nitrate crystal growth video.png

Minerals can be made out of the same element or they can be made out of multiple elements that have atomically bonded together.

Minerals form in a few different ways.

  • Minerals can form from magma/lava as it cools.  The slower it cools the more time a mineral has to crystallize and therefore the larger the mineral crystals can grow.  An example would be granite vs. basalt.  Granite cools off inside the Earth's crust and have a relatively long cooling period.  Basalt on the other hand cools off quickly as lava runs on the surface of the Earth.

 

Granite

Granite

 

 

Basalt

Basalt

 

  • Minerals can form from elements that are found in liquids.  One method of forming minerals is called precipitation and the mineral is considered to be an evaporite.  Evaporites occur when liquids evaporate precipitating elements and atoms that begin to bond forming elements which in turn form mineral crystals.  Evaporites are commonly found in ancient lakes and seabeds. Halite and gypsum are examples of evaporites.

Halite and Gypsum

Gypsum/Halite Mineral Crystals

Given enough time and plenty of space to grow, minerals can get really, really big.  Check out this cave that was found in Mexico.

Giant Crystal Cave Video.jpg

98% of the Earth's crust is made of only 8 elements.  However combining those elements together in different combination and you end up with 4000 minerals.  Still, there are really on a few dozen minerals that are common.  Most of the common minerals are in a group called the silicates, because they contain silicon and oxygen as well as one or more other elements.  The elements that pop up on the Earth the most are Oxygen, Silicon, Aluminum, Iron, Calcium, Sodium, Potassium and Magnesium.  If Mother Nature combines Iron, Oxygen, and Hydrogen together in just the right amount you might get Limonite.  Think of these elements as ingredients to cooking up minerals.

Limonite

Limonite

There are going to be two other activities that we are going to do.

1. Let's make our own Salt Crystals and see if we can combine the elements of Sodium and Chloride together to create an evaporite.

3. Let's take a few common minerals and break them down into their individual elements to see what ingredients Mother Nature used.