CrystalsA solid substance in which the particles, or pieces, are arranged in one of 6 repeatable patterns or shapes when molten minerals solidify or when the liquid evaporates from a solution.

Crystals have:

1. Definite shape

2. Purity (made of the same substance)

3. Each breaks along the weakest line/plane (crack)

Crystals Form in One of 6 Shapes

Cubic

How do you think a geologist might use crystals to identify minerals?

Do you think you can correctly identify the shape of each of your minerals?

It can be very difficult to identify the shape of the crystals in all of your minerals because not all samples will have well developed crystals. Geologists will sometimes have to use very sophisticated equipment to identify the crystals shape.

Class Activity

Each student will cut and tape one of each crystal shape.

Your teacher will then tape them all together to form mineral models.

Data Collection

Next use your magnifying glasses, I want you to examine your minerals and see if you can identify the shape of their crystals. Record your observations in your binder.

Video: http://vimeo.com/35097331

Crystal Shapes of Minerals

Cubic

 

Tetragonal Hexagonal

Orthorhombic

 

Monoclinic Triclinic

Examples

Salt Crystals

Salt crystals are referred to as a cubic crystal because they are a pattern of cubes.

The shape of a crystal is the repeating pattern of the particles that make it up. The salt crystals only have one pattern of crystals and they are cubic. Each mineral can contain only one crystal shape. The crystal shape of a mineral will be the same no mater where on earth you find that mineral. Salt crystals are cubic no matter where you find them.

Do your notes look like mine?