Granite Mortar and Pestle

Granite is a common type of intrusive, felsic, igneous rock which is granular and phaneritic in texture.
A worldwide average of the chemical composition of granite, by weight percent:

SiO2 72.04% (silica)
Al2O3 14.42% (alumina)
K2O 4.12%
Na2O 3.69%
CaO 1.82%
FeO 1.68%
Fe2O3 1.22%
MgO 0.71%
TiO2 0.30%
P2O5 0.12%
MnO 0.05%

It is not easy to measure the hardness of Granite. Granite is a rock composed of multiple minerals, typical Quartz, Feldspar, Biotite and Hornblende. Each of the minerals has a unique hardness. In other words, we can measure the hardness of individual material but not easy of granite as a rock.