If enough heat and pressure is applied (40000 to 60000 times atmospheric pressure and 900 to 1300 degrees Celsius), granite or any other allotrope of carbon can be turned into diamond.
gneiss
It would become metamorphic rock.
Heat and pressure cause granite to change to gneiss.
Gneiss is formed from pre-existing rocks that are subjected to intense directional pressure and heat, causing an alignment of their constituent minerals into parallel bands, a texture that is referred to as foliation.
when it is subject to great pressure
gneiss
Granite becomes metamorphic by being subjected to immense heat and pressure, turning into gneiss.
It would become metamorphic rock.
Granite does not turn into limestone. Granite is an igneous rock originating from volcanic activity. Limestone is a sedimentary rock laid down in the oceans millions of years ago. Limestone does turn into marble when subjected to huge pressures and heat. It is found areas with a lot of seismic activity like Itlay and Turkey.
slate
They both are formed by intense heat. However, metamorphic rocks are formed by intense heat and pressure, while igneous rocks are just dried lava/magma.
Heat and pressure
When emplaced granite is subjected to pressures and temperatures from mountain building processes due to tectonic plate movements, the component minerals are essentially realigned perpendicularly to the direction of the stress.
Heat and pressure
Through heat and pressure
Heat and pressure cause granite to change to gneiss.
Graphite has its own atomic structure of its basic carbon atoms. Subjecting it to very high temperature and pressure would not change its structure. Carbon, when subjected to very high temperature and pressure can be crystallized into diamond structures.