OBJECTIVES:

• Comparing two and three dimensional shapes
• Exploring the shapes of gems.

VOCABULARY:

• cube
• parallelogram
• prism
• rhombohedron
• square       
• triangle

MATERIALS:

• paper
• pencil
• Gem Kit
• Gemstone worksheet
• Swift GH microscopes (optional)

Students compare elements with compounds.

BACKGROUND:

Gems are attractive substances that people find valuable. Many minerals are gems, such as diamonds, but not all gems are minerals; amber is an example. Gems are "cut" into many different geometric shapes. In this exercise, students will begin to look at geometric shapes, and will also learn the differences between a gem and a mineral.

The world is three dimensional, but children usually draw only in two dimensions. In this exercise students also will learn the fundamentals of drawing basic three-dimensional shapes.

PROCEDURE:

1. Students must know the key components of mineral shapes to be able to distinguish and draw them. The chart below shows three basic geometric shapes that are common in minerals. Draw and label each two dimensional shape on the board, along with its three-dimensional equivalent. Demonstrate how to draw each object one at a time. Allow the students to draw along with you. Drawing intermediate forms will help you instruct the students on how to draw the shapes. Shading also helps students see the shapes as three-dimensional.

2. After the students have practiced making the three-dimensional shapes, hand out the gemstone placemats. The section "TYPES OF GEM CUTS" shows side-view pictures of the gems that are illustrated on the placemats. This may be difficult for third graders to visualize. The gem kit contains several examples of these gems; let the students handle the gems; this will help them make the connection. Impress on them that the shapes are cut and faceted by skilled craftsmen.
    

3. If you have a Swift GH microscope you may want to show the gems under higher magnification to the students.
     

4. Remember that not all gems are minerals. On the Gem worksheet there is an area called "ORGANIC GEMS," that are not minerals. The remaining gems on the placemat are minerals or mineraloids (opal). Students love to look and touch the gems. Be sure to remind the students to look for the shapes that they drew during the lab.

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