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Moh's Hardness Scale
shows the hardness of some common minerals; hardness is a property of minerals
Igneous, intrusive rock used as a building material because it is very durable and strong (ex. The Great Wall of China)
Igneous, extrusive rock- very light gray to a medium gray- contains a large number of gas bubbles- looks something like a sponge- very light weight- most pieces will float in water
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