That is an old classification and i am not sure the classification still exists.
Is granite the hardest rock.
These two stones have a mohs hardness rating of 6 or 7.
The other rocky planets mercury venus and mars are covered with basalt as is the ocean floor of earth but only earth has this beautiful and interesting rock type in abundance.
So we strive for the hardest most attainable and attractive option in stones which happens to be granite and quartz.
But in the 1960s when i began learning rock classification a quartzite was a sandstone that was composed predominantly of quartz and cemented with sili.
Marble is a degree or two less and though it is still a very hard stone it s rating on the mohs scale is about a 5.
Strictly speaking granite is an.
Granite ˈ ɡ r æ n ɪ t is a common type of felsic intrusive igneous rock that is granular and phaneritic in texture.
Granites can be predominantly white pink or gray in color depending on their mineralogy the word granite comes from the latin granum a grain in reference to the coarse grained structure of such a completely crystalline rock.
Granite comes in at a 6 to 7 on the mohs scale meaning it is relatively hard.
Granite is the signature rock of the continents.
An example of the hardness of a granite countertop can be seen in the fact that a knife blade will not scratch the surface.
The igneous rock is comprised of mostly quartz and feldspar along with smaller amounts of various other minerals.