Nanoindentation quantification of micro-mechanical properties for rock-forming minerals in monocrystalline and rock-hosted states

To investigate the correlation between the micro-mechanical properties of rock-forming minerals in their monomineralic and rock-hosted states, this study selects common rock-forming minerals—calcite, quartz, and feldspar (all in their monomineralic form)—as well as limestone (containing 78% calcite) and granite (containing 25% quartz and 65% feldspar) as research subjects. Nanoindentation tests were conducted to quantitatively characterize their micro-mechanical behavior. The results show that the elastic modulus of pure calcite and calcite in limestone are 72.0 ± 2.4 and 77.3 ± 3.2 GPa, respectively, with only a 6.9% difference; their hardness values are 1.7 ± 0.2 and 1.9 ± 0.1 GPa, with a 10.5% difference. The elastic modulus of pure quartz and quartz in granite are 100.1 ± 1.6 and 95.8 ± 5.2 GPa, respectively, differing by only 4.3%; their hardness values are 11.7 ± 1.0 and 11.1 ± 1.6 GPa, with a 5.1% difference. The elastic modulus of pure feldspar and feldspar in granite are 77.4 ± 1.7 and 71.7 ± 3.4 GPa, with a difference of 7.4%; their hardness values are 7.5 ± 0.8 and 7.2 ± 1.0 GPa, with a 4.0% difference. The micro-mechanical properties of monomineralic minerals are generally consistent with those observed in their rock-hosted states, indicating that such properties are primarily governed by the intrinsic characteristics of the crystal structure, while the influence of the surrounding rock matrix is relatively minor.