## 4 Results and Discussion  
### Elastic Wave Velocity  
Measured compressional and shear wave velocities for all 10 unaltered samples lie within the ranges 3375-4277 m/s and 1964-2534 m/s, respectively. Specimen-specific compressional wave velocities are as follows: albite 1 = 3837 m/s, albite 2 = 3697 m/s, albite 3 = 3886 m/s, albite 4 = 3745 m/s, quartz 1 = 3754 m/s, quartz 2 = 3,748 m/s, quartz 3 = 3375 m/s, biotite = 3928 m/s, calcite = 3837 m/s, and chlorite = 4277 m/s. Specimen-specific shear wave velocities are as follows: albite 1 = 2213 m/s, albite 3 = 2,242 m/s, albite 4 = 2222 m/s, quartz 1 = 2166 m/s, quartz 2 = 2162 m/s, quartz 3 = 2250 m/s, biotite = 1964 m/s, calcite = 2215 m/s, and chlorite = 2534 m/s. It is notable that the elastic wave velocity of chlorite is relatively high compared to that of quartz and biotite. Figure 6 shows that the elastic wave velocity in each sample gradually decreased as chemical and physical weathering proceeded. Post-weathering bulk compressional and shear wave velocities for all samples changed to 1665-2274 m/s and 832-1131 m/s, respectively. Specimen-specific reductions for compressional wave velocities are as follows: albite 1 = 55%, albite 2 = 38%, albite 3 = 43%, albite 4 = 50%, quartz 1 = 56%, quartz 2 = 49%, quartz 3 = 42%, biotite = 44%, calcite = 41%, and chlorite = 56%. Equivalent percentage decreases for shear wave velocities are as follows: albite 1 = 52%, albite 2 = 56%, albite 3 = 56%, albite 4 = 54%, quartz 1 = 62%, quartz 2 = 59%, quartz 3 = 61%, biotite = 49%, calcite = 51%, and chlorite = 55%.  
Figure 6: Measured elastic wave velocities for each sample: (**a**) albite 1, (**b**) albite 2, (**c**) albite 3, (**d**) albite 4, (**e**) quartz 1, (**f**) quartz 2, (**g**) quartz 3, (**h**) biotite, (**i**) calcite, and (**j**) chlorite.  
While compressional waves can propagate through fluids (e.g., air, water) and solids (e.g., minerals), shear waves can only be transmitted through the latter, making them useful for determining fabric characteristics within a rock [34; 35]. Reductions in compressional and shear wave velocities due to weathering (Figure 7) can be calculated via subtraction of a sample's pre- to post-weathering shear wave reduction from a sample's pre- to post-weathering compressional wave reduction. The average difference in reduction ratio for all 10 samples was approximately \(-8\%\), with the negative sign showing that weathering reduced the shear wave velocity to a proportionally greater degree than the compressional wave velocity. Both albite 2 and quartz 3 samples showed the greatest magnitude of change (around \(-19\%\)), which infers a high biotite (Mohs hardness scale \(\approx 2.5\)) and orthoclase (Mohs hardness scale \(\approx 6\)) content in each, giving the rocks an average Mohs hardness scale value of around 4 (cf. Figure 5). Of the samples albite 1, albite 2, albite 3, and albite 4, which have high albite content, albite 2 had the highest reduction ratio of \(-18\%\), because it has relatively sparse quartz (20.9%), which has a high Mohs hardness scale value of around 7, and relatively abundant biotite (10.7%), which has a low Mohs hardness scale value of around 2.5. Of the samples quartz 1, quartz 2, and quartz 3, the reduction ratio for quartz 2 was greatest (\(-18\%\)) due to its relatively sparse quartz (Mohs hardness scale \(\approx 7\)) and abundant orthoclase (Mohs hardness scale \(\approx 6\)).