Final answer:
Crystalline rocks such as granite have the highest bearing capacity, superior to gravel, silts, and clays, due to their solid composition and the stability they provide.
Step-by-step explanation:
The soil/rock type that has the highest bearing capacity is crystalline rock, such as granite. Granite is a type of igneous silicate rock that constitutes most of Earth's continental crust. Its composition provides it with superior strength and stability compared to other soil/rock types. In contrast, silt, although comprised of minerals like feldspar and silica, possesses fine particles that enhance its plasticity, particularly when water is added, which does not translate into high bearing capacity. Similarly, clay soils, known for their cohesive qualities stemming from fine particles and plasticity, generally have low bearing capacity due to their tendency to expand and contract which can lead to soil movement. On the other hand, gravel has a higher bearing capacity than silts or clays but is still surpassed by the solidity and strength of crystalline rocks like granite.