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 These holes are formed by the gases trapped inside when the rock is being formed.

 As this rock is very light, it can float on water.

 Pumice is quite often used as a decorative rock.

 It is also used as a body scrubber and to polish floors.

 Powdered pumice is required by Dentistto police Teeth.

3) Basalt

 Basalt is hard, dark, volcanic rock.

 It is formed when the lava flows from volcanoes or from cracks in the earth’s surface and then
hardens.
 The edges of the rock are very sharp.

 Basalt is dark in colour due to more content of iron and magnesium

 Basalt is used in the construction of building

 Basalt makes up most of the oceanic crust of the earth.

4) OBSEDIAN ROCK

 It is another type of igneous rock formed by the cooling of lava.
 It is usually black in color and have sharp edges.