The above rock is obsidian. It is an igneous rock that is formed from the cooling of magma/lava. It is found where ever there has been rhyolitic volcanoes. You can find it in the Western United States, predominantly. Yellowstone National Park has a mountainside containing the rock. Its chemical composition is 70-75% SiO2 and contains MgO and Fe3O4. It is used for surgical scalpels due to its smoothness, however, it is not recognized by FDA for this purpose.
This rock happens to be slate, a metamorphic rock. It is formed from the combination of rocks being compressed with low heat and pressure. Large deposits, and the slate industry, are found in Spain, Wales and in the United States in Pennsylvania. It is composed of quartz and either muscovite or illite primarily. One can also find biotite, chlorite, hematite and pyrite as well. It is used in the construction business for roofing, flooring and for monument and head stone pieces.
The rock shown above is sandstone. It is a sedimentary rock formed by the layering of sediments being exposed to pressure from weight above pressing down. Sandstone is often found in deserts and dried-up bodies of water. Large deposits can be found in the Sahara Desert and the Arabian Desert. It is composed quartz and/or feldspar, mostly. This is because they are the most common minerals in the Earth's crust. This does not limit them to being the only type of sandstone though.
This mineral is zoisite. It's chemical composition is Ca2Al3(SiO4)(Si2O7)O(OH). It can be found in metamorphic and pegmatitic rock. It is brittle, yet has a hardness greater than 6. It is found in Kenya, Norway, Pakistan and in the United States in Washington. It was formerly called saualpite.
*Pictures Courtesy of Google Images
*Information Courtesy of Wikipedia.org
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