Download Summer of Learning Activities: Geology: Groovy Granite

Activity: Groovy Granite
Theme: Geology
Ideal Group Size
Grade Level
Set Up/Clean Up Time
Activity Time
Small to Mid-size (up to 30)
All
2 min / 1 min
10 minutes
Math/science questions addressed: What is granite? How can the same type of rock look so different?
Overview: Participants examine different pieces of granite, all of which were pieces left over from
countertops installed in people’s houses. Granite is extremely varied in terms of crystal size, color and
mineral composition, which makes it really fun to look at!
Materials: 5 loose granite pieces, plus 5 granite pieces borrowed from the My Favorite Rock rock kits,
pencil and paper (optional), magnifying glasses
Set up: Pull granite pieces from My Favorite Rock kit bags.
To do: Give each group a piece of granite and 1 or 2 magnifying glasses. Give everyone time to look at
their granite pieces and those of neighboring groups.
Ask: How would you describe your rock? How many types of minerals (how many colors) do you see in
your piece of granite? How is your piece of granite different from your neighbors’?
Explain: Granite is an igneous rock, which means it is formed from volcanic material deep underground.
It’s basically cooled magma. The colors come from the different minerals that made up the magma. We
can tell by looking at granite whether the magma cooled slowly (large, chunky crystals) or quickly
(small, more homogenous crystals).
Ask: Do you think your rock cooled quickly or slowly? What about your neighbors’ rocks? Which one
cooled more quickly?
Explain: While it is nice to know what all the minerals in your rock are, it’s very difficult to tell without
specialized scientific equipment. Granite always contains quartz and feldspar. Beyond that, it can
contain many other minerals as well. In general, the clear-ish crystals (even tinted ones) tend to be
quartz, while white or gray opaque minerals are feldspar. Other common minerals are:

biotite or mica – flaky, shiny, black or silver

hornblende – opaque and black or dark gray

copper – turns granite green

iron – makes granite blacker or redder
Background: Granite is an igneous rock defined by its large crystals and contains both quartz and
feldspar. In the commercial sector, “granite” can include much more than that. In this activity, we have
included granite based on the commercial definition.
There are endless numbers of rocks with different mineral compositions, but here is an example of how
granite can include many different minerals came from the news:
Some home owners who had recently renovated their kitchens and were now trying to sell their homes
were having trouble because they were failing their radon tests. Radon tests measure radioactivity,
which can occur naturally in many parts of the country. The source of the radioactivity turned out to be
their brand new countertops which contained traces of uranium. Because of the rapidly expanding
market for granite countertops, mines were opening and shipping stone without always doing thorough
testing.
(See: The New York Times, “What’s Lurking in Your Countertop?” from July 2008)
A sample of granite.
These 2014 Summer Learning science activities were developed by Pacific Science Center