Is the rock light
colored and very light in weight compared
to other rocks of the same size? If yes,
your rock is probably pumice. Pumice is
mostly trapped air and may actually float
on water!
Matthew Nyman, TERC
Is the rock dark or reddish
colored and fairly light in weight compared
to other rocks of the same size? If yes,
your rock is probably scoria. Scoria is
frequently used in gas barbecue grills to
spread heat from the burner more evenly.
Matthew Nyman, TERC
Is the rock dark colored and fairly heavy
compared to other rocks of the same size? If yes, your rock is probably
basalt. Basalt may also have vesicles, holes where volcanic gases were
trapped in the cooling lava.
If you have identified your sample, return to the beginning
of the rock identification
key, select another rock sample, and begin the process
over again.
If your rock sample does not have any of the features
described on this page, reexamine the rock with a hand
lens or magnifying glass. Look at the sample from all
angles. Concentrate on fresh surfaces where you might
be able to better determine the texture. Return to the
beginning of the rock identification
key and start over again.
