Pumice rock is the lightest and only rock that can float on water due to cooling very fast underground, which left it very light with many holes. It has a rough texture and is used to rub off dead skin. Granite is one of the most common rocks on Earth's surface, used for countertops and buildings. It cooled slowly, resulting in similarly sized crystals as marble. Basalt is very hard and forms from lava; it cooled quickly but with small crystals. Obsidian forms from volcanic glass and was historically used for tools since it is very sharp when fractured. Scoria is a volcanic rock that cooled partially underwater, leaving it with holes like pumice.

2. Pumice rock

3. Pumice
The pumice rock is the lightest rock in the world and is the only
rock in the world that can float in the water. It can float in the
water because of the special way it was cooled. The pumice rock
cooled very fast therefore it is very light and that it also cooled
underwater that causes the holes in the rock. People use the
rocks for rubbing of dead skin from their feet. It looks a bit like
coral. It has a very rough texture and that’s why they use it to
rub off dead skin. Pumice is also used as insolation or as a hand
soap ingredient.

4. Granite

5. Granite
Granite as said before is similar to marble and is also used for
kitchen countertops and floors or statues. Granite is the most
used rock for everyday life for example most buildings have
granite in it. A lot of pebbles on the ground are granite. Like
marble it is cooled very slowly and has almost the exact same
sized crystals as marbles. Granite is the most common rock on
the earths surface. Granite has a pretty rough texture. People
sometimes use granite for rock climbing walls.

6. Basalt

7. Basalt
Basalt is very smooth and hard rock that is made when
volcanoes spit out pieces of lava. Basalt is also very common on
the earths surface like granite but is the most common rock
underground. Basalt has very small crystals so it cooled very
quickly but not as quickly as pumice which doesn’t have crystals
at all. Basalt can be found on the Moon, Mars and even Venus.
Since Basalt is very hard people used to very often use basalt as
a grinding stones for mills to make wheat out of grains. Basalt is
very often used for asphalt.

8. Obsidian

9. Obsidian
Obsidian is a very smooth and shiny rock that is also known as
natural glass. A lot of people used to use obsidian to make
arrowheads or fishing hooks because it can be very sharp. A
lot of surgeons today use obsidian knives for eye surgery or
other things. The stone aged people often wanted obsidian
because it was sharper than flint and was very practical back
then. Obsidian also cools very slowly so it has few crystals
even though it is very shiny. Obsidian is very brittle and
therefore can be chipped very easily, which is why the stone
aged wanted it. Obsidian sometimes come very rarely colored
blue, yellow, red or orange.

10. Scoria

11. Scoria
Scoria is a red, brown, or black and is also referred to volcanic
rock. Scoria was cooled a bit slower then pumice but also
underwater that is why it has holes in it like the pumice rock. The
name scoria comes from the Greek and means rust, probably
because it can be red as rust as seen below in the picture. Scoria
is often used in high temperature isolations, and landscaping and
drainage works. Some statues on Easter Island have scoria in
them.

12. Facts

13. Facts
• Igneous rocks are the most common rocks used for buildings
• Mount Rushmore is made out of igneous rocks
• The word igneous comes from the Latin and means
fire, because igneous rocks come from volcanos.
• Did you know that basalt which is an igneous rock is one of
the heaviest and densest rocks in the world.
• Did you know that most of the Empire State Building is made
of igneous rocks.
• Thousands of years ago people carved their homes out of soft
igneous rocks.