Sedimentary, Metamorphic, and Igneous rocks.
Rock Name: Serpentinite
How it is classified: Green, rough, and heavy.
How it is formed: Through the process of serpentinization.
Where it is mostly found: Rochester, Vermont, USA
How the rock is used: Sculptures, jewelry, and other decorative purposes.
Rock name: Obsidian
How it is classified: Glassy, shiny, smooth or rough, black.
How it is formed: When felsic lava extrudes from a volcano, cooling quickly.
Where is it mostly found: Around active Volcanoes. For example: Argentina, the U.S., Australia, etc.
How the Rock is used: a knives, spear tips, etc.
Rock Name: Dolomite
How it is classified: "A calcium magnesium carbonate"
How it is formed: Dolomite crystals fill pores in their host Rock.
Where it is mostly found: Most European areas, Africa, and Canada
How the Rock is used: The stone, not the mineral, has many uses. One being in the construction industry: The Rock is crushed and used as a road base, an aggregate for asphalt, etc. It is also used in the chemical industry and the farming industry.