that would be granite.
A smooth, black rock is likely to be basalt. Basalt is an extrusive igneous rock that is commonly dark in color and has a fine-grained texture, giving it a smooth appearance.
Slate rock has a fine-grained texture, with individual mineral grains that are too small to be seen with the naked eye. This gives slate a smooth and dense appearance.
Metamorphic rock can vary in texture, with some being rough due to the presence of mineral grains and others being smooth due to recrystallization of minerals during the metamorphic process. The texture of metamorphic rock depends on factors such as the original rock type and the intensity of heat and pressure.
Silt is composed of fine particles, smaller than sand but larger than clay. When silt becomes compacted and cemented together over time, it forms a type of sedimentary rock called siltstone. Siltstone typically has a smooth texture and can range in color from gray and brown to white.
A weathered rock is usually smooth and broken down from erosion over time. A rock that is not weathered is usually rough, with jagged edges. NB: A lot depends on the type of rock.
Shale
bumpy and smooth
smooth
A smooth, black rock is likely to be basalt. Basalt is an extrusive igneous rock that is commonly dark in color and has a fine-grained texture, giving it a smooth appearance.
The rock is the type of music with electric guiters, drums, and singing. The other rock is just smooth and bumpy
A conglomerate.
A rock that is heavy and silky could potentially be anthracite, which is a type of coal known for its high density and smooth, shiny appearance. Another possibility could be serpentine, a metamorphic rock that can have a slick, smooth surface due to its high content of the mineral serpentine.
The rock described could be any number of possibilities. There is just not enough information on the sample description to identify it. Look at a rock and mineral book at the library or go online and type in "rock identification" in the search engine, and you'll have a much better chance at finding out what it is.
It is abrasion
brown also it might be heavily soiled clothes
Blackboards are typically made of a type of rock called slate. Slate is a fine-grained metamorphic rock that is easily split into thin, smooth sheets, making it ideal for writing on with chalk.
Slate rock has a fine-grained texture, with individual mineral grains that are too small to be seen with the naked eye. This gives slate a smooth and dense appearance.