BACKGROUND:
Minerals are either composed of one type of element (a native mineral)
or two or more elements (a compound). The characteristics of minerals
depend on their constituent elements and compounds. Table salt (the
mineral halite) would not have the same properties if either sodium or
chlorine were replaced with another element such as silver or potassium.
However, the characteristics of elements are not always expressed in
minerals; for example, quartz, a hard, glassy mineral, is composed of
silicon, which is a lightweight, metallic element, and oxygen, a clear
gas.
In this exercise, the students will be given the characteristics of
several elements, and will then identify those characteristics in a
group of minerals. They will learn that elements cannot always be
recognized in minerals.
PROCEDURE:
- Pass out the Periodic Table Placemats Instruct students to find the
following elements on the placemats: iron (Fe), sulfur (S), copper (Cu),
silicon (Si), and titanium (Ti). Ask the students to say the atomic
symbol of each element. Review the characteristics of each element as
outlined below. Have students record the names of the elements in their
workbooks.
IRON: heavy, metal
SULFUR: yellow, bad "rotten egg" smell
COPPER: blue-green as a compound with oxygen, copper color as a
native metal
SILICON: gray, glassy, metallic, light weight
TITANIUM: dark gray or silvery, metallic
- Explain the lab. The students should try to determine if the
characteristics of the elements described in class are recognizable in
the specimens. In other words, the students should try to decide if the
individual pieces provide clues to which element they are examining.
- Allow the students to look at the mineral samples and try to determine
which elements are in which sample. Students should record their guesses
in the squares provided on the worksheet.
 Here are answers to guide their observations:
quartz (rose) Si + O, a trace of Ti (gives it the pink color)
even though titanium is gray
sulfur S, is naturally yellow and if scratched gives a bad smell
(rotten egg)
pyrite Fe + S, called fools’ gold; heavy from Fe and yellow from S
hematite Fe + O, heavy from Fe
chrysocolla Cu + Si + O, blue from copper tarnish
copper Cu, color is natural copper
bornite Cu + Fe + O, color from copper, heavy from iron
- Have the students write an answer to the conclusion. Make sure they
understand that elements are not always identifiable in minerals.
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