Name _____________________
Building Blocks of Common Minerals
Background information
range of radius ratio (rc/ra)
0.155- 0.225
0.225-0.414
0.414-0.732
0.732-1.00
1.00
geometric shape of anions
around the cation
equilateral triangle
tetrahedron
octahedron
cube
closest packing
number of anions around
the cation(CN)
3
4
6
8
12
1. Measure the diameter of the Styrofoam ball. ____ mm.
2. Measure the diameter of the red fuzzy ball _____ mm.
3. One represents an anion and one represents a cation. Which is the
cation?________________
4. Given these two “atoms”, what is the rc/ra ratio?__________
5. What is the geometric shape that can best form with your model atoms?
6. You will use the red pipe cleaners to hold together the Styrofoam balls, which
will represent oxygen atoms. What kind of atomic bonds do the red pipe cleaners
represent?
7. How many bonds can one oxygen atom make?____
8. The fuzzy ball will represent a silicon atom. How many bonds can a silicon atom
make?_____
9. Create a geometric building block of silicate minerals. What is the formula of the
building block____________
10. What is the overall charge of the building block?______
11. What will happen when two building blocks are placed next to each other?
12. What kind of ion could be used to get two building blocks to hold together?
13. Place 5 or more building blocks on the table. Use the green fuzzy balls to
represent iron ions. Place them in locations that will allow the building blocks to
stick together as a mineral. What is the formula for this mineral ________
14. What kind of bonds are represented by the attraction of the fuzzy balls to the
building blocks?
15. The name of this mineral is olivine. Replace half of the iron with magnesium
(gold fuzzy balls). This is another form of olivine, with the formula (FeMg)SiO4
Olivine can also exist with all magnesium. Any mineral that can exhange cations
in and proportion yet maintain the same structure is said to be a solid solution.
16. Remove one oxygen atom from one tetrahedron (yes, they are called
tetrahedrons!) and join it with a covalent bond to another tetrahedron. Continue
the process until you have made a chain using up half of the tetrahedrons. Make
a second chain. Will these chains repel each other?_________
17. What can be used between two adjacent chains to hold them together?_________
18. Minerals composed of single chains of silicates are members of a group called
pyroxenes. One common pyroxene is the mineral augite. Would it be easier the
break the model along the covalent bonds or along the ionic bonds?_________
19. A mineral that has weakness in its geometric structure because of differential
directions of bonding is said to have cleavage planes. Would pyroxenes have
cleavage planes?________ Would
olivine have cleavage planes?________
20. Look at diagrams other silicate
structures. Which structure has the most
covalent bonds between tetrahedrons?
21. Which structure would need the fewest
cations to hold together the adjacent
tetrahedrons.
22. What is the formula for quartz?_______
23. Would you expect quartz to have
cleavage planes?_______