Limestone
![Picture](/uploads/1/4/0/2/14021357/6151183.jpg?0)
One of its uses is making paper white. It is composed of calcite. The density of limestone is usually a 2.5 to 2.7 cubic centimeters.
Gneiss
![Picture](/uploads/1/4/0/2/14021357/597731.jpg?0)
One of its uses is flooring. It is gray or pink with dark streaks. The texture is rough.
http://geology.com/rocks/pictures/limestone-tufa-380.jpg
http://wiki.answers.com/Q/What_are_the_uses_of_limestone
http://www.graniteforus.com/characteristics/granite-characteristics.html
http://www.ehow.com/list_7608531_physical-characteristics-limestone.html
http://hyperphysics.phy-astr.gsu.edu/hbase/geophys/geopic/gneiss99.jpg
http://wiki.answers.com/Q/What_is_a_use_for_Gneiss_rock
http://www.rocks-rock.com/gneiss.html
http://volcano.oregonstate.edu/vwdocs/vwlessons/lessons/Metrocks/Picture1.gif
http://www.physicalgeography.net/fundamentals/images/gneiss.jpg
http://archive.ck12.org/ck12/images?id=113732
http://wiki.answers.com/Q/What_are_the_uses_of_limestone
http://www.graniteforus.com/characteristics/granite-characteristics.html
http://www.ehow.com/list_7608531_physical-characteristics-limestone.html
http://hyperphysics.phy-astr.gsu.edu/hbase/geophys/geopic/gneiss99.jpg
http://wiki.answers.com/Q/What_is_a_use_for_Gneiss_rock
http://www.rocks-rock.com/gneiss.html
http://volcano.oregonstate.edu/vwdocs/vwlessons/lessons/Metrocks/Picture1.gif
http://www.physicalgeography.net/fundamentals/images/gneiss.jpg
http://archive.ck12.org/ck12/images?id=113732